JP2010249898A - Light diffusion film and surface light source using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion film which attains compatibility between unevenness-eliminated luminance and enhanced luminance in a thin and direct-type surface light source, and the thin, high-luminance and direct-type surface light source using the light diffusion film. <P>SOLUTION: The light diffusion film has a layer (hereinafter called an internal diffusion layer (ID layer)) consisting of a matrix resin containing diffusion elements (D), wherein the ratio of the diffusion elements (d1) satisfying the following conditions (1) and (2) to the full number of the diffusion elements (D) contained in the internal diffusion layer (ID layer) is ≥50% and the number of the diffusion elements (D) contained in the internal diffusion layer (ID layer) in the thickness direction of the light diffusion film is 3-120 pieces. Condition (1) is that the absolute value (¾Nm-Nd¾) of a difference between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and that Nd of the diffusion elements (d1) is 0.05-0.3 and condition (2) is that the flatness degree is 3-100. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a diffusion sheet suitable for a surface light source of various display devices, particularly a liquid crystal display device, and a surface light source using the diffusion sheet.

  Liquid crystal display devices are used in various applications such as notebook computers and mobile phone devices, televisions, monitors, car navigation systems, and the like. The liquid crystal display device incorporates a surface light source serving as a light source, and is structured such that light from the surface light source is controlled by a liquid crystal cell. The characteristic required for this surface light source is not only as a light source for emitting light, but also to make the entire screen shine brightly and uniformly.

  The structure of the surface light source can be roughly divided into two. One is a method called a side light type surface light source. This is a method mainly used for, for example, a notebook personal computer or the like that is required to be thin and small, but is characterized by using a light guide plate as a basic configuration. In the case of a sidelight type surface light source, a fluorescent tube is installed on the side surface of the light guide plate, light is incident on the light guide plate from the side surface, and light is propagated throughout the surface while totally reflecting inside the light guide plate. A part of the light is removed from the total reflection condition by diffusing dots or the like applied to the back surface of the light, and the light is collected from the front surface of the light guide plate, thereby functioning as a surface light source. In the case of a sidelight type surface light source, in addition to these configurations, a reflection film that functions to reflect and reuse light leaking from the back surface of the light guide plate, and a diffusion sheet that equalizes the light emitted from the front surface of the light guide plate Many types of optical films are used, such as a prism sheet for improving the front luminance.

  Another method is a method called a direct type surface light source. This is a system that is preferably used for television applications that require large size and high brightness. FIG. 4 is a cross-sectional view of the direct type surface light source cut in the vertical direction. The casing of the surface light source is covered with the reflecting plate 10 so that one surface is open, and the fluorescent tube 20 is disposed inside the casing. In the opening, a plurality of optical film groups 40 are arranged on the diffusion plate 30 to form a surface light source. As the reflecting plate 10, for example, a white polyester sheet containing fine bubbles therein is preferably used. The light source 20 uses a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL) as a linear light source, and a light emitting diode (LED) as a point light source. These linear or dot light sources are made uniform by the diffuser plate 30 and the optical film group 40 installed thereon to form a planar light source.

  This type of surface light source can accommodate a large screen by arranging a plurality of light sources in the back of the screen, and can secure sufficient brightness. However, brightness unevenness (brightness unevenness) occurs in the screen due to the light source installed at the back of the screen, which is also a feature. That is, the light above the light source is bright and the space between adjacent light sources is dark. For this reason, in the direct type surface light source, in order to eliminate this luminance unevenness, a light diffusing plate (milky white plate) having extremely strong light diffusibility is installed on the upper side of the fluorescent tube to make the screen uniform (patent) Reference 1). The light diffusing plate is a light diffusing plate made of an acrylic resin or a polycarbonate resin in which fine particles are dispersed. This light diffusing plate eliminates uneven brightness and makes the screen uniform. However, because it diffuses strongly, the total light transmittance is low and the light utilization efficiency deteriorates. As a result, the required front brightness is insufficient. Therefore, only a light diffusing plate does not completely eliminate luminance unevenness, but a plurality of optical films such as a diffusing sheet exhibiting a light collecting effect in the front direction while diffusing light isotropically on the diffusing plate. This is intended to eliminate luminance unevenness (Patent Document 2). This diffusion sheet is a sheet called a bead sheet in which a diffusion layer containing fine particles such as organic cross-linked particles is formed on a base material sheet. Unlike a light diffusion plate, this diffusion film is an optical film that exhibits a certain degree of directivity in the front direction. It is. In addition, a prism sheet or the like is incorporated in order to further improve the light collecting property as necessary.

  In recent years, these liquid crystal display devices are required to be thin from the viewpoints of space saving, light weight, design, and the like, and to reduce the number of light sources mounted for cost reduction. In such a configuration, in the conventional configuration, the conventional optical film is used for the optical film group (reference numeral 40 in FIG. 4), and the effect of uniformizing the light per sheet is low, so it is difficult to eliminate luminance unevenness. As a result, the luminance is uneven just above and between the light sources, and the image of the light source is visually recognized. Therefore, in order to eliminate the luminance unevenness and make it uniform (erasing the unevenness), it was necessary to install a large number of optical films. However, there is a problem that the thickness of the surface light source is increased, which is solved. As a means, a film including a spherical diffusion element has been proposed (Patent Document 3).

JP 2004-29091 A JP 2001-324607 A JP 2001-272508 A

  In direct type surface light sources, multiple light sources are installed at intervals in the back of the screen, so when the thickness is reduced and the space between the diffuser and the light source is narrowed, or when the number of light sources is reduced, the luminance unevenness increases. It has become difficult to eliminate it. Therefore, in the conventional optical sheet, the number of sheets to be used is increased in order to eliminate the uneven brightness. However, even if the uneven brightness is not solved sufficiently, the brightness is large even if the unevenness is resolved. As a result, it is difficult to eliminate both luminance unevenness and increase luminance.

  Therefore, in view of the background of such prior art, the object of the present invention is a light diffusing film that can achieve both elimination of uneven brightness and high brightness even in a thin direct type surface light source and a direct type surface light source having a small number of light sources, Another object of the present invention is to provide a direct-type surface light source that is thin, low-cost, and high in brightness.

The present invention employs the following means in order to solve such problems. That is, the light diffusion film of the present invention is
1. A film having a layer made of a matrix resin containing a diffusion element (D) (hereinafter referred to as an internal diffusion layer (ID layer)), the total number of diffusion elements (D) included in the internal diffusion layer (ID layer) The ratio of the number satisfying the following (1) and (2) of the diffusion element (d1) is 50% or more, and the number of the diffusion elements (D) included in the internal diffusion layer (ID layer) in the film thickness direction is 3. A light diffusing film having at least 120 but not more than 1.
(1) The flatness is 3 or more and 100 or less.
(2) The absolute value | Nm−Nd | of the difference in refractive index between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and the refractive index Nd of the diffusion element (d1) is 0.1 or more and 0.00. 3 or less.
2. 2. The light diffusing film according to 1, wherein the number of diffusion elements (D) per 10 μm length in the film thickness direction is 1/10 μm or more and 10/10 μm or less,
3. In a cross section parallel to the film surface, the ratio of the in-plane long axis length of the diffusing element (D) to the in-plane length (in-plane short axis length) perpendicular to the long axis direction (in-plane long axis) The light diffusion film according to 1 or 2, wherein the length / in-plane minor axis length) is 2 or less,
4). The light diffusion film according to any one of 1 to 3, wherein the volume occupancy of bubbles in the internal diffusion layer (ID layer) is 3% by volume or less,
5). The light diffusion film according to any one of 1 to 4, wherein the internal diffusion layer (ID layer) is biaxially oriented,
6). The light diffusion film according to any one of 1 to 5, wherein the matrix resin constituting the internal diffusion layer (ID layer) is a thermoplastic resin containing a polyester resin,
7). The light diffusing film according to any one of 1 to 6, wherein the diffusing element (d1) is made of a thermoplastic resin,
8). The light diffusing film according to 7, wherein the diffusing element (d1) is a polyolefin resin,
9. The light diffusion film according to any one of 1 to 8, wherein the surface free energy of at least one surface is 35 mN / m or more,
10. The resin layer (S layer) is laminated on one side or both sides of the internal diffusion layer (ID layer), and the difference (Tm1−Tm2) between the melting point Tm1 of the matrix resin and the melting point Tm2 of the resin layer (S layer) is The light diffusion film according to any one of 1 to 9, which is 10 ° C or higher,
11. The light diffusion film according to any one of 1 to 10 having an uneven structure on at least one surface,
12 The light diffusion film according to any one of 1 to 11, wherein the total light transmittance is 25 to 80%,
13. A surface light source using the light diffusion film according to any one of 1 to 12,
It is.

  According to the present invention, it is possible to provide a light diffusing film capable of eliminating luminance unevenness and increasing luminance, and by incorporating this into a surface light source of a liquid crystal display device, particularly a direct type surface light source, When the thickness is reduced or the number of light sources is reduced, it is possible to achieve both high screen uniformity and high luminance characteristics.

It is explanatory drawing of the measuring method of the long-axis length in a cross section perpendicular | vertical to the film surface of a diffusion element (d1), and a short-axis length. It is explanatory drawing of the measuring method of the long-axis length in a cross section perpendicular | vertical to the film surface of a diffusion element (d1), and a short-axis length. It is explanatory drawing of the measuring method of the long-axis length in a cross section perpendicular | vertical to the film surface of a diffusion element (d1), and a short-axis length. It is a figure which shows an example of a direct type | mold surface light source. It is a perspective view of the conventional film containing a spherical diffusion element. It is explanatory drawing of the behavior of light when light collides with a spherical diffusion element. It is explanatory drawing of the behavior of the light in the direct type | mold surface light source carrying the film of FIG. It is a perspective view of the film of this invention containing a flat diffusion element (d1). It is explanatory drawing of the behavior of light when light collides with a flat diffusion element (d1). It is explanatory drawing of the behavior of the light in the direct type | mold surface light source carrying the film of FIG. It is explanatory drawing of the measuring method of the in-plane long-axis length in a cross section parallel to the film surface of a spreading | diffusion element (d1), and an in-plane short-axis length. It is explanatory drawing of the measuring method of the in-plane long-axis length in a cross section parallel to the film surface of a spreading | diffusion element (d1), and an in-plane short-axis length. It is explanatory drawing of the measuring method of the in-plane long-axis length in a cross section parallel to the film surface of a spreading | diffusion element (d1), and an in-plane short-axis length. It is a perspective view which shows a light-diffusion layer typically. It is a perspective view which shows a light-diffusion layer typically. It is a perspective view which shows a light-diffusion layer typically. It is a perspective view which shows a light-diffusion layer typically. It is a perspective view which shows a light-diffusion layer typically. It is the figure which showed typically the shape of the light-diffusion layer used in the Example and the comparative example.

  The light diffusing film of the present invention includes an internal diffusion layer (ID layer) containing at least an incompatible component as a diffusion element (D) with respect to a matrix resin (hereinafter referred to as matrix resin). Consists of. Here, the diffusion element (D) means that the absolute value | Nm−Nd | of the difference between the refractive index Nm of the matrix resin and the refractive index Nd of the diffusion element (D) is 0.03 or more.

In the light diffusion film of the present invention, the diffusion element (D) included in the internal diffusion layer (ID layer) includes a diffusion element (d1) that satisfies the following (1) and (2).
(1) The absolute value | Nm−Nd1 | of the difference in refractive index between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and the refractive index Nd1 of the diffusion element (d1) is 0.05 or more and 0.0. 3 or less.
(2) The flatness is 3 or more and 100 or less.

  In addition, the flatness of the diffusing element (D) is obtained by procedures (A1) to (A4) described later.

  Moreover, in the light diffusion film of the present invention, the diffusion element (d1) is contained in an amount of 50% or more based on the total number of diffusion elements (D) included in the internal diffusion layer (ID layer).

  In the light diffusion film of the present invention, the number of diffusion elements (D) included in the internal diffusion layer (ID layer) in the film thickness direction is 3 or more and 120 or less.

  In addition, the number of the diffusing elements (D) in the film thickness direction is obtained by procedures (B1) to (B5) described later.

  By satisfying all the above requirements, it can be useful as a light diffusing film for a liquid crystal display surface light source, particularly a film excellent in luminance and unevenness in a direct type surface light source. The reason will be described in detail below.

  Since the light diffusing film of the present invention includes a flat diffusing element (d1) having a refractive index different from that of the matrix resin, the light diffusing film (D) of the diffusing element (D) is compared with a conventional film including only a spherical diffusing element. Even if the volume occupancy is the same, the probability of collision of light increases, and as a result, transmitted light is easily diffused uniformly.

  Further, the light colliding with the diffusing element is scattered by being reflected / refracted at the interface between the matrix resin and the diffusing element. The behavior at that time will be described with reference to FIGS.

  FIG. 8 is a light diffusing film of the present invention in which the matrix 200 contains the flat diffusing element (d1) 100. FIG. 9 shows the light incident on the flat diffusing element (d1) 100 in the film of FIG. It is a figure which shows the behavior at the time of doing. Even if light λ0 incident on the flat diffusing element (d1) 100 is repeatedly reflected / refracted by the interface, light λ0 transmitted from the shape or light that is reflected by the interface and scattered toward the incident direction side. (Λ2) is almost all, and there is almost no light (λ3) scattered near the direction perpendicular to the incident direction. Therefore, the light that propagates in the in-plane direction of the film and exits from the end face of the film is lost. FIG. 10 is a view when the light diffusion film of the present invention is used as the surface light source film 41. As shown in the figure, the amount of light (λ3 ′) emitted from the side surface of the film and lost can be reduced. it can. As shown in FIG. 10, the light (λ2) reflected at the interface and scattered toward the incident direction is returned to the light source. Then, the light is reflected by the reflecting plate 10 and again enters the light diffusion film of the present invention (this phenomenon is sometimes referred to as “reuse of light”). In addition, when light is reused, the light is diffusely reflected by the reflective film 10, so that by repeating this cycle, the amount of light emitted from the surface light source can be made uniform in the surface. . As a result, luminance unevenness can be eliminated and uniformed (erasured). From the above mechanism, it is possible to achieve both high brightness and high non-uniformity compared with a diffusion film including a conventional spherical diffusion element (D).

  In addition, although the light-diffusion film of this invention expresses a high non-uniformity even if it is used for any part of the some optical film group 40 of FIG. 4, the optical film just on a diffuser plate at the point that the effect is high. It is more preferable to use as 41 in that the backscattered light can be used effectively and the brightness can be increased.

  Here, in the light diffusing film of the present invention, the diffusing element (d1) is more preferably 60% or more, further preferably 70% or more, particularly preferably 80% or more, with respect to the total number of diffusing elements (D). Preferably it is 90% or more. If the content of the diffusing element (d1) is less than 50%, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may be lowered.

  Also, the absolute value | Nm−Nd1 | of the difference in refractive index between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and the refractive index Nd of the diffusion element (d1) is more preferably 0. 1 or more and less than 0.25, more preferably 0.15 or more and less than 0.25, and particularly preferably 0.17 or more and less than 0.23. If the absolute value | Nm−Nd1 | of the refractive index difference between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and the refractive index Nd1 of the diffusion element (d1) is less than 0.05, the interface As a result of less refraction / reflection at the surface, the diffusivity may be reduced and it may be difficult to eliminate unevenness of brightness, and if it exceeds 0.3, the diffusivity becomes too strong and the direction perpendicular to the incident direction. This is not preferable because the light λ3 scattered in the vicinity increases and the luminance may decrease, or the light transmittance may decrease and the luminance may decrease.

  The flatness of the diffusing element (d1) is more preferably 5 or more and 50 or less, further preferably 10 or more and 30 or less, and particularly preferably 12 or more and 25 or less. If the flatness is less than 3, the amount of light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may decrease, and if the flatness exceeds 100, the diffusivity decreases and luminance unevenness occurs. Is not preferable because it may be difficult to eliminate the light, and the light transmittance may be reduced to lower the luminance.

Here, in order to include a diffusion element (d1) having a flatness of 3 or more and less than 100, when inorganic particles or organic crosslinkable particles are used as the diffusion element (d1), the flatness is 3 or more and 100. A method using particles controlled to a range can be mentioned. When a thermoplastic resin is used as the diffusing element (d1), a sheet in which a thermoplastic resin is dispersed as a diffusing element in a matrix is used.
1 ′) uniaxial or biaxial stretching so that the area stretching ratio is 1.5 times or more,
2 ′) rolling in the thickness direction so that the rolling rate is 90% or more,
3 ′) Combine 1 ′) and 2 ′) above,
And the like. Details of the method 1 ′) will be described later. The area magnification is obtained by multiplying the draw ratio of the first axis by the draw ratio of the second axis. In the method 2 ′), the rolling ratio (%) is obtained by dividing the thickness after rolling by the thickness before rolling and multiplying by 100.

In the light diffusing film of the present invention, in order to increase the flatness when using a thermoplastic resin as the diffusing element (d1),
1 ") Increase area stretch ratio or rolling rate,
2 ") A thermoplastic resin to be a diffusion element is finely dispersed in a matrix.
3 ″) The difference between the elastic modulus of the thermoplastic resin serving as the diffusion element at the glass transition temperature of the matrix resin + 25 ° C. and the elastic modulus of the matrix resin is reduced.
4 ") using at least two methods 1") to 3 ") above,
Such a method is preferably used.

  In the light diffusion film of the present invention, the number of diffusion elements (D) in the film thickness direction is more preferably 7 or more and 100 or less, and further preferably 13 or more and 60 or less. If the number of diffusing elements (D) in the film thickness direction is less than 3, light cannot be diffused sufficiently, and the unevenness in luminance when incorporated in a surface light source may be insufficient, which is preferable. If the number is 120 or more, the light transmission efficiency is insufficient, and the luminance when incorporated in a surface light source may be greatly reduced. In the light diffusing film of the present invention, by setting the number of diffusing elements (D) to 3 or more and 120 or less, it becomes possible to impart diffusivity without reducing the light transmission efficiency. When incorporated, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  In the light diffusing film of the present invention, the number of diffusing elements (D) per unit length in the film thickness direction is preferably 1/10 μm or more and 10/10 μm or less. More preferably, it is 1.2 pieces / 10 μm or more and 9 pieces / 10 μm or less, 1.5 pieces / 10 μm or more and 8 pieces / 10 μm or less, and further preferably 2 pieces / 10 μm or more and 7 pieces / 10 μm or less. If the number of diffusing elements per unit length in the film thickness direction is less than 1/10 μm, the light diffusibility with respect to light incident from an oblique direction will decrease, and uneven brightness will occur from the oblique direction when incorporated in a surface light source. Since it may be visually recognized, it is not preferable, and when it exceeds 10/10 μm, the distance between the diffusing elements becomes approximately the same as the wavelength of visible light. This is not preferable because it may decrease or the transmitted light may be colored, and the luminance when incorporated in a surface light source may be greatly decreased, or the color tone of the surface light source may be greatly changed. In the light diffusing film of the present invention, the number of diffusing elements per unit length is 1/10 μm or more and 10/10 μm, so that light can be diffused even from an oblique direction without reducing the light transmission efficiency. As a result, when incorporated in a surface light source, it is possible to eliminate luminance unevenness in an oblique direction without lowering luminance or changing color tone.

  In the light diffusing film of the present invention, the average flatness of the diffusing element (D) contained in the internal diffusion layer (ID) layer is preferably 3 or more and 100 or less. If the average flatness of the diffusing element (D) is less than 3, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction may increase and the luminance may decrease, and if the average flatness exceeds 100, It is not preferable because the diffusibility is lowered and it becomes difficult to eliminate unevenness of brightness, or the light transmittance is lowered and the brightness is lowered. In the present invention, by making the average flatness of the diffusing element (D) contained in the internal diffusion layer (ID) layer be 3 or more and 100 or less, it becomes possible to impart diffusibility without reducing light utilization efficiency. As a result, when incorporated in a surface light source, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  Moreover, in the light-diffusion film of this invention, it is preferable that the average major axis length a of a diffusion element (D) is 0.5 micrometer or more and 25 micrometers or less. More preferably, they are 1 micrometer or more and 20 micrometers or less, More preferably, they are 3 micrometers or more and 15 micrometers or less, Most preferably, they are 4 micrometers or more and 15 micrometers or less. If the average major axis length a of the diffusing element (D) is less than 0.5 μm, the average major axis length a of the diffusing element (D) becomes smaller than the wavelength of the light to be diffused, so that the light diffusibility is not good. This is not preferable because it may be insufficient and uneven luminance when incorporated in a surface light source may be insufficient. On the other hand, if the average major axis length a of the diffusing element (D) is 30 μm or more, the shape is flat. The diffusibility may be reduced, the light transmission efficiency may be reduced, and the luminance when incorporated in a surface light source may be greatly reduced. In the light diffusion film of the present invention, when the average major axis length a of the diffusion element (D) is 0.5 μm or more and 30 μm or less, it becomes possible to impart diffusibility without reducing the light transmission efficiency, As a result, when incorporated in a surface light source, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  In the light diffusing film of the present invention, the average thickness d of the diffusing element (D) is preferably 0.01 μm or more and 1 μm or less. More preferably, they are 0.1 micrometer or more and 1 micrometer or less, More preferably, they are 0.2 micrometer or more and 0.9 micrometers or less, Most preferably, they are 0.3 micrometer or more and 0.8 micrometers or less. If the average thickness d of the diffusing element (D) is less than 0.1 μm, the incident light is not recognized as the diffusing element (D), the light diffusibility is lowered, or the light beam is deactivated due to the thin film interference, and the luminance If the thickness exceeds 1 μm, the number of diffusing elements (D) in the thickness direction decreases, resulting in a decrease in light diffusivity, and unevenness in luminance when incorporated in a surface light source cannot be eliminated. This is not preferable because it may be sufficient. In the light diffusing film of the present invention, when the average thickness of the diffusing element is 0.01 μm or more and 1 μm or less, it becomes possible to impart efficient light diffusibility without deactivation of light, and when incorporated into a surface light source Therefore, it is possible to efficiently eliminate the luminance unevenness without reducing the luminance.

  In the light diffusing film of the present invention, the diffusing element (D) has an in-plane major axis length and an in-plane minor axis perpendicular to the major axis direction in a cross section parallel to the film surface. The length ratio (in-plane long axis length / in-plane short axis length) is preferably 2 or less. The ratio of the in-plane long axis length to the in-plane short axis length is obtained by procedures (C1) to (C7) described later.

  The ratio of the in-plane long axis length to the in-plane short axis length (in-plane long axis length / in-plane short axis length) is more preferably 1.5 or less, and still more preferably 1.2 or less. If the ratio of the in-plane long axis length to the in-plane short axis length (in-plane long axis length / in-plane short axis length) exceeds 2, the diffusibility decreases and the non-uniformity disappears. There are cases where there is a limitation when installing on a liquid crystal display due to non-uniformity and different brightness. In the light diffusing film of the present invention, the ratio of the in-plane long axis length to the in-plane short axis length (in-plane long axis length / in-plane short axis length) is set to 2 or less, over all directions, It becomes possible to have high diffusibility.

  In this invention, it is preferable that the volume occupation rate of the diffusion element (D) in an internal diffusion layer (ID) is 0.1 volume% or more and less than 25 volume%. The volume occupancy of the diffusing element (D) can be obtained by procedures (D1) to (D4) described later. The volume occupation ratio of the diffusing element (D) is more preferably 0.5% by volume or more and 20% by volume, further preferably 1% by volume or more and 15% by volume or less, and more preferably 1.5% by volume or more and 10% by volume. It is particularly preferable that the ratio be 2% by volume or more and 10% by volume or less. If the volume occupancy is less than 0.1% by volume, the diffusibility may be reduced and it may be difficult to eliminate unevenness of brightness. If the volume occupancy is 25% by volume or more, the light transmittance is reduced and the brightness is decreased. Since it may decrease, it is not preferable. In the light diffusion film of the present invention, by making the content of the diffusion element (D) contained in the internal diffusion layer (ID layer) 0.1 volume% or more and 25 volume% or less, without reducing the light utilization efficiency. It is possible to impart diffusibility, and as a result, it is possible to efficiently eliminate luminance unevenness and increase luminance when incorporated in a surface light source.

  In the light diffusion film of the present invention, it is preferable that bubbles (voids) are not contained in the internal diffusion layer (ID layer) as much as possible, and the volume occupation ratio is preferably 3% by volume or less. More preferably, it is 2 volume% or less, More preferably, it is 1 volume% or less. The volume occupancy rate of the bubbles can be obtained by procedures (E1) to (E4) described later. The volume occupancy of the bubbles is preferably 2% by volume or less, more preferably 1% by volume or less, and particularly preferably 0.5% by volume or less. If the volume occupancy exceeds 3% or more, light is unnecessarily scattered by the bubbles, and as a result, the amount of light λ3 scattered in the vicinity of the incident direction increases and the luminance may decrease. Therefore, it is not preferable. In the light diffusing film of the present invention, by making the volume occupancy of the bubbles 3% by volume or less, it becomes possible to impart diffusibility without reducing the light utilization efficiency. As a result, when incorporated into a surface light source In addition, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  In the light diffusion film of the present invention, the resin serving as a matrix of the internal diffusion layer (ID layer) is polyethylene terephthalate, polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, polylactic acid, polycyclohexylene dimethylene terephthalate, or the like. Polyester resins, polyolefin resins such as polyethylene, polystyrene and polypropylene, polyamide resins, polyimide resins, polyether resins, polyesteramide resins, polyetherester resins, acrylic resins, polyurethane resins, polycarbonate resins Examples thereof include resins and polyvinyl chloride resins. Among them, polyester resins, polyolefin resins, polyamide resins, acrylic resins or these are particularly preferred because of the variety of monomer types that can be copolymerized and the ease of adjusting the material properties. It is preferably formed mainly from a thermoplastic resin selected from these mixtures. In particular, polyester resins are more preferable in terms of mechanical strength, heat resistance, etc. Among these, polyester resins containing ethylene terephthalate as a main constituent component are more preferable from the viewpoints of transparency, moldability, and heat resistance. .

  In the light diffusing film of the present invention, it is also preferred that the polyester resin is a resin that serves as a matrix of the internal diffusion layer (ID layer). Examples of such copolymer components include dicarboxylic acid components such as malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, Aliphatic dicarboxylic acids such as methylmalonic acid, ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, alicyclic dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1 , 4-Naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5 -Sodium sulfoisophthalate Acid, phenylendandicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, dicarboxylic acids such as 9,9'-bis (4-carboxyphenyl) fluorenic acid or the like, or ester derivatives thereof, carboxy of the dicarboxylic acid component Representative examples include dicarboxy compounds in which oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, and a combination of a plurality of such oxyacids are added to the terminal. It is not limited. Moreover, these may be used independently or may be used in multiple types as needed.

  Examples of the diol component include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Alicyclic diols such as cyclohexanedimethanol, spiroglycol and isosorbide, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxyphenyl) fluorene, Representative examples include diols such as aromatic diols and the like, and dihydroxy compounds in which a plurality of these diols are connected, but are not limited thereto. Moreover, these may be used independently or may be used in multiple types as needed.

  Examples of the compound having a carboxylic acid or carboxylic acid derivative skeleton and a hydroxyl group in one molecule include oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives and oxyacids thereof. And the like, and the like.

  Here, in the light diffusing film of the present invention, it is preferable that the resin serving as the matrix of the internal diffusion layer (ID layer) contains at least a crystalline resin (A). By including at least the crystalline resin (A) as the matrix resin, orientation crystallization can be performed by stretching and heat treatment, and a light diffusion film having excellent mechanical strength and heat resistance can be obtained. Here, in crystalline resin, in accordance with JIS K7122 (1999), an exothermic peak accompanying melting is observed in a differential scanning calorimetry chart of 2ndRUN obtained by the procedures (F1) to (F4) described later. It is a resin. More specifically, a resin having a crystal melting heat amount ΔHm obtained from a peak area accompanying melting of 1 J / g or more is defined as a crystalline resin. In the light diffusing film of the present invention, among the resins constituting the matrix of the internal diffusion layer (ID layer), when the crystalline resin is one kind, the resin is the crystalline resin (A). When a plurality of crystalline resins constituting the matrix are included, the crystalline resin that is the main component of the crystalline resins is referred to as crystalline resin (A). In the light diffusing film of the present invention, the crystalline resin (A) is preferably a resin having a heat of crystal fusion ΔHm of 5 J / g or more, more preferably 10 J / g or more, and even more preferably 15 J / g or more. . By setting the crystal melting heat amount of the crystalline resin (A) in the above-mentioned range in the light diffusing film of the present invention, it becomes possible to further enhance orientation crystallization by stretching and heat treatment, and as a result, more mechanical strength and heat resistance can be achieved. It can be set as the outstanding light-diffusion film.

  In the light diffusion film of the present invention, the resin species constituting the matrix may be a mixture of a crystalline resin and an amorphous resin. In that case, it is preferable from the viewpoint of heat resistance and mechanical strength that the ratio of the total crystalline resin in 100% by mass of the resin constituting the matrix is 80% by mass or more.

  When a copolymerization component is introduced into the crystalline polyester resin (A) used in the light diffusion film of the present invention, it is performed within a range where the crystallinity does not disappear. As a method for introducing the copolymer component, the copolymer component may be added at the time of polymerization of the raw material polyester pellets and used as pellets in which the copolymer component has been polymerized in advance, or, for example, polybutylene terephthalate Thus, a method may be used in which a mixture of pellets polymerized alone and polyethylene terephthalate pellets is supplied to an extruder and copolymerized by transesterification during melt kneading.

  In the light diffusing film of the present invention, examples of the material of the diffusing element (D) include inorganic particles, crosslinkable resin particles, and thermoplastic resins incompatible with the matrix resin (hereinafter referred to as incompatible resins). Are also preferably used. When using inorganic fine particles or crosslinkable resin particles, it is possible to easily obtain a light diffusing film that satisfies the above-mentioned requirements by using, as the diffusing element (d1), particles whose shape is controlled in advance so as to be in the above-mentioned range. it can. Further, when an incompatible resin is used as the particles of the diffusing element (D), the flatness of the diffusing element (d1) is suppressed while suppressing generation of bubbles by cost, filter filterability, and a method described later. The diffusion element (d1) is more preferable than the inorganic fine particles and the crosslinkable resin particles because it can be easily obtained.

  In the light diffusion film of the present invention, when inorganic particles or crosslinkable particles are used as the diffusion element (D), examples thereof include glass, silica, barium sulfate, titanium oxide, magnesium sulfate, magnesium carbonate, calcium carbonate, talc. And inorganic particles such as clay, or crosslinkable resin particles obtained by crosslinking acrylic resin, organic silicone resin, polystyrene, polyolefin, polyester, urea resin, formaldehyde condensate, fluororesin, and the like.

  In the light diffusing film of the present invention, when an incompatible resin is used as the diffusing element (D), specific examples thereof include copolymerized polyester resin, polyethylene, polypropylene, polybutene, polymethylpentene, cyclopentadiene, and the like. Linear, branched or cyclic polyolefin resin, polyamide resin, polyimide resin, polyether resin, polyesteramide resin, polyetherester resin, acrylic resin, polyurethane resin, polycarbonate Resin, polyvinyl chloride resin, polyacrylonitrile, polyphenylene sulfide, polystyrene, fluorine resin and the like. Among them, especially from polyester resins, polyolefin resins, polyamide resins, acrylic resins, or mixtures thereof because of the variety of monomer types to be copolymerized and the ease of adjusting the material properties. It is preferably formed mainly from a selected thermoplastic resin. These incompatible resins may be a homopolymer or a copolymer, and two or more incompatible resins may be used in combination.

  Specifically, when a polyester resin is used as the matrix resin of the internal diffusion layer (ID layer), the incompatible resin includes a polyolefin resin, a polyamide resin, a polyimide resin, a polyether resin, and a polyester. Preferred examples include amide resins, polyether ester resins, acrylic resins, polyurethane resins, polycarbonate resins, and polyvinyl chloride resins. Among these, incompatible resins include linear, branched or cyclic polyolefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, and cyclopentadiene, and acrylics such as poly (meth) acrylate. A resin, polystyrene, a fluorine resin, or the like is preferably used. These incompatible resins may be a homopolymer or a copolymer, and two or more incompatible resins may be used in combination. Among these, polyolefin is preferably used in terms of transparency, heat resistance, and refractive index. Specifically, polypropylene, polymethylpentene, cycloolefin copolymer and the like are preferably used because they have particularly high heat resistance.

  In the light diffusing film of the present invention, when an incompatible resin is used as the diffusing element (D), the dynamic storage elastic modulus at the glass transition temperature of the resin serving as the matrix of the internal diffusion layer (ID layer) is 500 MPa or less. It is preferable that The glass transition temperature here is a glass transition temperature Tg in a temperature rising process (temperature rising rate: 20 ° C./min) obtained by differential scanning calorimetry (hereinafter referred to as DSC), and more specifically, JIS K-7121 ( (1999 version), it is obtained by the procedures (F1) to (F4) described later.

  The dynamic storage elastic modulus is a value obtained by preparing a sheet having a thickness of 200 μm and obtaining the sheet by a method according to JIS K-7244 (1999 edition). Specifically, the temperature dependence under the measurement conditions of tensile mode, sample dynamic amplitude speed (driving frequency) is 1 Hz, distance between chucks is 5 mm, strain amplitude is 10 μm, initial value of force amplitude is 100 mN, and heating rate is 2 ° C./min. This is a value obtained when (temperature dispersion) is measured.

  The dynamic storage elastic modulus at the glass transition temperature of the resin serving as the matrix of the internal diffusion layer (ID layer) of the incompatible resin serving as the diffusion element (D) is more preferably 250 MPa or less, still more preferably 200 MPa or less, Particularly preferred is 100 MPa or less, and most preferred is 50 MPa or less. When the dynamic storage elastic modulus exceeds 500 MPa, by the method described later, deformation at the time of stretching becomes difficult, and as a result of interfacial peeling is likely to occur, air bubbles may be easily formed and light transmittance may be reduced, It is not preferable because it is difficult to form a flat shape, and the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, which may reduce the luminance. In the light diffusing film of the present invention, when an incompatible resin is used as the diffusing element (D), the dynamic storage elastic modulus at the glass transition temperature of the resin serving as the matrix of the internal diffusion layer (ID layer) is 500 MPa or less. This makes it possible to easily form an internal diffusion layer (ID layer) having a flat diffusion element (d1), and the obtained film can impart diffusivity without reducing the light utilization efficiency. As a result, when incorporated in a surface light source, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  In the light diffusing film of the present invention, when an incompatible resin is used as the diffusing element (D), the MFR of the resin is preferably 1 g / 10 min or more. The MFR here is a value measured under a load of 5 kg at a temperature of the melting point of the resin serving as a matrix of the internal diffusion layer (ID layer) + 5 ° C. based on ASTM-D1238 (1999). . The melting point of the resin serving as the matrix of the internal diffusion layer (ID layer) is the melting point Tm in the heating process (heating rate: 20 ° C./min) obtained by DSC based on JIS K-7121 (1999). Specifically, it is a value obtained by the following methods (F1) to (F4).

  More preferably, the MFR of the incompatible resin serving as the diffusion element (D) is 20 g / 10 min or more, and further preferably 100 g / min or more. If the MFR is 1 or more, it cannot be sufficiently finely dispersed in the resin serving as the matrix of the internal diffusion layer (ID layer), and as a result, the resulting film may have reduced light diffusibility.

  In the light diffusion film of the present invention, when a polyester resin is used as the matrix resin of the internal diffusion layer (ID layer), the incompatible resin used as the diffusion element (D) includes a carboxylic acid ester group, maleic anhydride It preferably contains a resin having a substituent such as a group, an oxazoline group, an epoxy group, or an oxetane group (hereinafter referred to as a modified incompatible resin (b2)). By containing the modified incompatible resin (b2), it reacts with the polyester resin at the time of melt-kneading to form a block copolymer compound by the method described later. Further, when used in combination with an unmodified incompatible resin, it intervenes near the interface between the polyester resin and the unmodified incompatible resin. As a result, peeling at the interface between the polyester resin and the incompatible resin in the stretching step is suppressed, and the incompatible resin can be co-stretched, whereby the inside having the substantially flat diffusion element (d1) inside A diffusion layer (ID layer) can be formed.

  The modified incompatible resin (b2) used in the light diffusing film of the present invention can be obtained by graft copolymerization of a compound having the above substituent when, for example, a polyolefin resin is used as the incompatible resin.

  For example, when a carboxylic acid ester or maleic anhydride group is introduced, it can be obtained by graft copolymerization with an unsaturated carboxylic acid. In order to graft copolymerize an unsaturated carboxylic acid with a polyolefin resin, the polyolefin resin is dissolved or suspended in an organic solvent, and then the unsaturated carboxylic acid is added to the decomposition temperature of the radical generator (generally, The temperature can be raised to 50 ° C. or higher and 150 ° C. or lower, and a radical generator can be added little by little to cause a graft reaction. Alternatively, a method may be used in which an unsaturated carboxylic acid, which is a graft monomer, is grafted onto a polyolefin resin together with a radical generator in an extruder as necessary (for example, 150 ° C. or more and 260 ° C. or less) for graft polymerization.

  In addition, unsaturated carboxylic acid is used by the concept containing not only the unsaturated compound which has -COOH group but ester and anhydride which are its derivatives. Examples of unsaturated carboxylic acids include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid; unsaturated carboxylic acid esters such as methyl methacrylate, methyl acrylate and butyl fumarate; And acid anhydrides such as acid anhydrides and itaconic acid anhydrides. Of these, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, and itaconic anhydride are preferred. In particular, acrylic acid, maleic acid, and maleic anhydride are polyesters that are productive and incompatible resins. This is preferable in that it can be finely dispersed in the resin.

  Moreover, when introducing an oxazoline group, an epoxy group, an oxetane group, etc., it is obtained by graft-polymerizing the compound which has this substituent and an unsaturated bond. In addition, after graft polymerization of an ester bondable derivative of an unsaturated carboxylic acid and a compound having the above-mentioned substituent, or after preparing a modified incompatible resin obtained by graft polymerization of an unsaturated carboxylic acid, the unsaturated carboxylic acid and the above-mentioned substitution It can also be obtained by an esterification reaction with a compound having a group.

  In the light diffusing film of the present invention, when the incompatible resin includes an unmodified incompatible resin and a modified incompatible resin (b2) having a carboxylic acid ester or a maleic anhydride group introduced, the acid value thereof is It is preferable to set it to 1 KOHmg / g or more and 80 KOHmg / g or less. In addition, in this invention, an acid value means the acid value prescribed | regulated by JIS-K0070-1992. More preferably, they are 2 KOHmg / g or more and 60 KOHmg / g or less, More preferably, they are 3KOHmg / g or more and 60KOHmg / g or less, Especially preferably, they are 5KOHmg / g or more and 60KOHmg / g or less, Most preferably, they are 5KOHmg / g or more and 40mg / g or less. By setting the acid value within the above range, the co-stretchability of the polyester resin that is the matrix resin of the internal diffusion layer (ID layer) and the incompatible resin that is the diffusion element (D) can be increased. The flatness of the diffusing element (d1) can be further increased while suppressing the generation of bubbles. In addition, the incompatible resin can be very finely dispersed in the polyester resin.

  When the acid value of the modified incompatible resin (b2) is less than 1 KOH mg / g, the polyester resin and the incompatible resin may not be co-stretched. As a result, the flatness of the incompatible resin diffusing element cannot be increased, or voids may be generated around the incompatible resin in the stretching process. In this case, the light is unnecessarily scattered by the bubbles, and as a result, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may be lowered.

  In addition, if the acid value of the modified incompatible resin exceeds 80 KOHmg / g, the heat resistance of the incompatible resin is lowered, and when melt-extruded, it is decomposed in the extruder and the decomposed product causes a film defect. Even if the heat resistance of the incompatible resin is not lowered, the polyester resin as the matrix resin is severely deteriorated, and film formation itself may be difficult.

  In addition, when the light diffusion film of the present invention contains only the carboxylic acid ester and the modified incompatible resin (b2) introduced with maleic anhydride groups, the acid value of the modified incompatible resin (b2) is 0.001 KOHmg / g. The amount is preferably 20 KOHmg / g or less. More preferably, it is 0.01 KOHmg / g or more and 15 KOHmg / g or less, More preferably, it is 0.1KOHmg / g or more and 10KOH or less. By setting the acid value within the above range, the co-stretchability of the polyester resin that is the matrix resin of the internal diffusion layer (ID layer) and the incompatible resin that is the diffusion element (D) can be increased. The flatness of the diffusing element (d1) can be further increased while suppressing the generation of bubbles. In addition, the incompatible resin can be very finely dispersed in the polyester resin.

  If the acid value of the modified incompatible resin (b2) is less than 0.001 KOH mg / g, the polyester resin and the incompatible resin may not be co-stretched. As a result, the flatness of the incompatible resin diffusing element cannot be increased, or voids may be generated around the incompatible resin in the stretching process. In this case, the light is unnecessarily scattered by the bubbles, and as a result, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may be lowered.

  On the other hand, if the acid value of the modified incompatible resin (b2) exceeds 20 KOHmg / g, the heat resistance of the incompatible resin is lowered, and when melt-extruded, it is decomposed in the extruder, and the decomposed product has a film defect. Even if the heat resistance of the incompatible resin does not decrease, the polyester resin, which is a matrix resin, deteriorates severely, making film formation itself difficult. .

Moreover, in the light-diffusion film of this invention, it is preferable that the acid value of the whole incompatible resin is 0.001 KOHmg / g or more and 20 KOHmg / g or less. By setting the acid value within such a range, the incompatible resin can be dispersed extremely finely in the polyester resin.
If the acid value of the incompatible resin is less than 0.001 KOH mg / g, the polyester resin and the incompatible resin may not be co-stretched. As a result, the flatness of the incompatible resin diffusing element cannot be increased, or voids may be generated around the incompatible resin in the stretching process. In this case, the light is unnecessarily scattered by the bubbles, and as a result, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may be lowered.

  In addition, when it exceeds 20 KOHmg / g, the heat resistance of the incompatible resin is lowered, and when melt extrusion is performed, the resin is decomposed in the extruder and the decomposed product may cause a film defect or the heat resistance of the incompatible resin. Even if the properties are not lowered, the polyester resin, which is a matrix resin, is severely deteriorated and film formation itself may be difficult.

  In the light diffusing film of the present invention, when an unmodified incompatible resin and a modified incompatible resin (b2) are included as the incompatible resin, the modified incompatible resin (b2) is converted into an unmodified incompatible resin. It is preferable to make it contain in the ratio of 2 to 45 mass parts with respect to 100 mass parts of resin. If the content of the modified incompatible resin (b2) is less than 2 parts by mass relative to 100 parts by mass of the unmodified incompatible resin, the incompatible resin can be sufficiently finely dispersed in the polyester resin. In addition, the polyester resin and the incompatible resin may not be co-stretched in the stretching step. In this case, the light is unnecessarily scattered by the bubbles, and as a result, the light λ3 scattered in the vicinity of the vertical direction with respect to the incident direction increases, and the luminance may be lowered.

  Further, when the content of the modified incompatible resin (b2) exceeds 45 parts by mass with respect to 100 parts by mass of the unmodified incompatible resin (b1), it is decomposed in the extruder during melt extrusion, and decomposed. For film production, the product may cause film defects, or even if the heat resistance of the incompatible resin does not decrease, the polyester resin, which is a matrix resin, is severely degraded, making film formation itself difficult. There is a case where it is not preferable, and the light diffusibility tends to be lowered because the diffusing element (D) is finely dispersed. In the case where only the modified incompatible resin (b2) and the polyester resin are contained in the internal diffusion layer (ID layer) without containing the unmodified incompatible resin, the one having a high degree of modification is used. The same phenomenon occurs, and the productivity and practicality may be extremely inferior.

  In the light diffusing film of the present invention, when an incompatible resin is used as the diffusing element (D), the content thereof is preferably 0.1% by mass or more and 25% by mass or less with respect to the internal diffusion layer (ID layer). More preferably, it is 0.5 mass% or more and 20 mass% or less, More preferably, it is 1 mass% or more and 15 mass% or less, Most preferably, it is 1.5 mass% or more and 10 mass% or less, Most preferably, it is 1.5 mass% or more 8 It is below mass%. If the content is less than 0.1% by mass, the diffusibility may be reduced and it may be difficult to eliminate unevenness of brightness. If the content is 25% by mass or more, the light transmittance is reduced and the luminance is lowered. This is not preferable. In the light diffusing film of the present invention, by making the content of the incompatible resin 0.1% by mass or more and 25% by mass or less, it becomes possible to impart diffusibility without reducing the light use efficiency. As a result, when incorporated in a surface light source, it is possible to efficiently eliminate luminance unevenness and increase luminance.

  In the light diffusion film of the present invention, an appropriate additive in an amount that does not impair the effects of the present invention as necessary, for example, a heat stabilizer, an oxidation stabilizer, an ultraviolet ray, is included in the internal diffusion layer (ID layer). Fillers such as inorganic particles and organic resin particles that contain an absorber, ultraviolet stabilizer, nucleating agent, dye, dispersant, coupling agent, etc., or whose difference from the refractive index of the resin used as the matrix is 0.1 or less May be blended.

  The internal diffusion layer (ID layer) of the light diffusion film of the present invention is formed from the above-described configuration and materials, and the thickness is generally preferably 10 μm or more and 500 μm or less. More preferably, they are 20 micrometers or more and 300 micrometers or less, More preferably, they are 50 micrometers or more and 250 micrometers or less. When the film thickness is less than 10 μm, the film may be easily broken during film formation, or the light diffusibility tends to be lowered, and it may be difficult to eliminate the luminance unevenness. On the other hand, when the film thickness exceeds 500 μm, it may be difficult to wind the film into a roll shape, or the light transmittance may be lowered and the luminance may be lowered.

  The light diffusion film of the present invention may be a single film consisting only of the internal diffusion layer (ID layer), or may be a laminated film in which other layers are laminated. That is, another resin layer (S layer) may be laminated on one side or both sides of the internal diffusion layer (ID layer). In particular, when surface processing such as coating is performed using the obtained film, a polyester layer (P layer) that does not contain the diffusing element (D), more preferably a biaxially stretched polyester layer is used due to its workability. A laminated film laminated on at least one surface is a preferred embodiment. Moreover, when shape | molding the surface using a metal mold | die using the obtained film, the laminated | multilayer film by which the resin layer which has a moldability is laminated | stacked at least on the metal mold | die surface becomes a preferable aspect from the workability etc. .

  When the light diffusion film of the present invention is a laminated film, the internal diffusion layer (ID layer) thickness (if there are a plurality of internal diffusion layers (ID layers), the inner diffusion layer (ID layer) ) And the sum of the thicknesses of the other resin layers ((the thickness of the internal diffusion layer (ID layer) / the sum of the thicknesses of layers other than the ID layer) = (lamination ratio)) Can be arbitrarily set depending on the intended use, but is preferably 5/1 or more, more preferably 8/1 or more, from the viewpoint of obtaining high light diffusibility. By adopting such a configuration, it is possible to impart processability to the surface while having high light diffusibility.

  Moreover, it is preferable that the thickness of the light-diffusion film of this invention is generally 10 micrometers or more and 500 micrometers or less. More preferably, they are 20 micrometers or more and 300 micrometers or less, More preferably, they are 50 micrometers or more and 250 micrometers or less. If the film thickness is less than 10 μm, the film may be easily broken at the time of film formation, the light diffusibility tends to be reduced, and it may be difficult to eliminate the uneven brightness, or the light diffusion film for a surface light source When incorporated into a display, the film does not have a self-supporting property, and the film may sag, resulting in uneven brightness of the display. On the other hand, when the film thickness exceeds 500 μm, it may be difficult to wind the film into a roll shape, or the light transmittance may be lowered and the luminance may be lowered.

  Moreover, it is preferable that the surface free energy of at least one surface of the light-diffusion film of this invention is 35 mN / m or more. More preferably, it is 38 mN / m or more, More preferably, it is 40 mN / m or more. When it is less than 35 mN / m, surface treatment is performed using the obtained film by coating or the like (for example, when a light diffusion layer (D layer) is formed by a coating method as described later). Even when coating unevenness is formed during the formation of the coating film or it can be formed uniformly, the adhesion to the coating film may be reduced. In the light diffusing film of the present invention, by setting at least one surface free energy to −35 mN / m, it is possible to impart formability when processing the film and adhesion to the formed layer.

  In the light diffusion film of the present invention, when a laminated resin layer (S layer) is laminated on one side or both sides of the internal diffusion layer (ID layer), the melting point Tm1 of the matrix resin of the internal diffusion layer (ID layer) And the difference (Tm1−Tm2) in the melting point Tm2 of the resin layer (S layer) is preferably 10 ° C. or more. By adopting such a configuration, it becomes possible to impart moldability to the S layer using the internal diffusion layer (ID layer) as a support, and as will be described later, a light diffusion layer (D layer) or back coat Layer shapes and the like can be easily formed.

  Moreover, the light-diffusion film of this invention may laminate | stack the layer (C layer) which has another function using a well-known technique in the range which does not lose the effect of this invention as needed. Examples include a light diffusing layer containing spherical particles, a condensing layer, a polarizing separation layer, an antireflection layer, a light reflecting layer, a flame retardant layer, a cushion layer, an antistatic layer, an ultraviolet absorbing layer, a hard coat layer, and an adhesive layer. Gas barrier layer, and the like.

  The light diffusing film of the present invention has a flat diffusing element as an internal diffusing layer (ID layer), so that it has high brightness and high unevenness even by itself. It is also a preferable form to form a light diffusion layer (D layer) having Examples of the light diffusing layer include those having irregular irregularities 500 in which the binder resin 300 includes fine particles 400 (FIG. 14), and geometric irregularities 500 such as a transfer layer using a mold. And the like (FIG. 15), the binder resin 300 containing the fine particles 400 and having the geometric unevenness form 500 (FIG. 16), and combinations thereof. By forming the surface irregularities like these, it is possible to have both the diffusibility due to the refraction of light by the internal diffusion layer (ID layer) and the light condensing by the lens effect due to the light diffusion layer (D layer). Thus, the light diffusibility can be further improved and the brightness can be increased.

  In the light diffusing film of the present invention, the cross-sectional shape of the surface irregularity shape is a shape obtained by cutting out a half of a substantially spherical shape as shown in FIG. 17A, and a sinusoidal shape as shown in FIG. Etc. These may have different heights and pitches as shown in FIGS. 17 (c) and 17 (d), or may have an irregular shape as shown in FIG. 17 (e). Further, in the case of the geometric surface form 500, these shapes in the film plane are arranged in a substantially dome shape as shown in FIG. 18 (a), or as shown in FIG. 18 (b). Either a substantially rugby ball-shaped array or a striped array extending in one direction as shown in FIGS. 18C and 18D can be preferably used. . Further, FIG. 18B shows a case where the long axes of rugby balls are arranged in one direction, but the arrangement direction may be random.

  In the light diffusion layer (D layer) formed on the light diffusion film of the present invention, when the fine particles 400 are used, the volume average particle diameter R is preferably 0.1 μm or more and 30 μm or less. In addition, when the cross-sectional shape of the fine particles 400 is not a perfect circle, the value is converted to a perfect circle having the same area. More preferably, they are 0.2 micrometer or more and 20 micrometers or less, Most preferably, they are 0.3 micrometer or more and 10 micrometers or less. When the volume average particle size R of the fine particles 400 is smaller than 0.1 μm, the scattering and reflection phenomenon may depend on the wavelength, and as a result, the transmitted light is colored or accumulated to form the uneven shape 6. However, the desired light diffusibility may not be obtained, which is not preferable. Further, when the volume average particle size R of the fine particles 400 is larger than 30 μm, the light diffusion efficiency is deteriorated, which is not preferable. In the light diffusion film of the present invention, when the volume average particle size R of the fine particles 400 is 0.1 μm or more and 30 μm or less, it becomes easy to control to a desired light diffusibility without coloring transmitted light. The material may be organic particles such as polymethyl methacrylate, polystyrene, and copolymers thereof, inorganic particles such as polysilicon, silica, and titanium oxide, and organic-inorganic composite materials.

  The surface of the light diffusion layer (D layer) preferably has irregularities, and the glossiness, which is a measure of the irregularities, is preferably 50 or less, more preferably 40 or less, and particularly preferably 30 or less. The glossiness here is 60 ° glossiness measured based on JIS Z8741 (1999 edition). By setting the gloss level within the above range, light diffusibility can be further improved, unevenness elimination can be further improved, and luminance can be increased. Further, the ratio Gmax / Gmin between the glossiness Gmax in the direction in which the glossiness of the light diffusion layer (D layer) is the largest and the glossiness Gmin in the direction in which the glossiness is the smallest is preferably 2 or less. More preferably, it is 1.5 or less. By setting the gloss ratio Gmax / Gmin in the above range, a film having high unevenness canceling property in any direction can be obtained regardless of the direction of the film and the observation angle. The thickness of the light diffusion layer (D layer) is not particularly limited, but is preferably 1 μm or more and 20 μm or less, and more preferably 1 μm or more and 10 μm or less. In addition, the light diffusion layer (D layer) has various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, and an organic solvent within the range that does not impair the effects of the present invention. Lubricants, pigments, dyes, fillers, antistatic agents and nucleating agents may be blended.

  The transmittance of the light diffusion film of the present invention is preferably 25% or more and 80% or less. More preferably, they are 30% or more and 80% or less, More preferably, they are 35% or more and 75% or less, Especially preferably, they are 45% or more and 75% or less. If the transmittance is less than 30%, the light transmittance may be too low and the brightness may decrease. If the transmittance exceeds 80%, too little light is returned into the surface light source, In some cases, the uniforming effect is too small, and it is difficult to eliminate luminance unevenness. In the light diffusing film of the present invention, when the transmittance is 25% or more and 80% or less, both high luminance and high unevenness extinction can be achieved.

  The haze of the light diffusion film of the present invention is preferably 70% or more. More preferably, it is 80% or more, More preferably, it is 85% or more, Most preferably, it is 90% or more. If the haze is less than 70%, light diffusibility may be insufficient and it may be difficult to eliminate luminance unevenness. In the light diffusing film of the present invention, by setting the haze to 70% or more, good non-uniformity can be exhibited. In addition, although an upper limit is not specifically limited, 100 (%) becomes a substantial upper limit.

  Next, although an example is demonstrated about the manufacturing method of the light-diffusion film of this invention, this invention is not limited only to this example. In order to form the internal diffusion layer (ID layer), a film-forming apparatus having an extruder (main extruder) is used, and a thermoplastic resin and a diffusion element (D) that are sufficiently vacuum-dried as necessary are used. A mixture containing at least a composition containing (inorganic particles and / or crosslinkable resin particles and / or unmodified incompatible resin and / or modified thermoplastic resin) is supplied to a heated extruder. The addition of the raw material of the diffusing element (D) may be performed by using a master chip prepared by uniformly melting and kneading in advance, or may be supplied directly to a kneading extruder. From the viewpoint of the dispersibility of the diffusion element (d1), a master batch prepared by melt-kneading in advance using a twin-screw extruder is used, or a film is formed directly after melt-kneading in a twin-screw extruder. preferable. Further, particularly when an incompatible resin is used as the diffusing element (d1), in order for the formed film to satisfy the requirements of the present invention, the average dispersion diameter during kneading is previously determined using a twin screw extruder. It is more preferable to control within the range of 0.5 μm or more and 10 μm or less. More preferably, they are 0.8 micrometer or more and 8 micrometers or less, More preferably, they are 1 micrometer or more and 5 micrometers or less, Most preferably, they are 1 micrometer or more and 3 micrometers or less. If you do not use a twin screw extruder, the dispersion diameter in the film will vary, thereby reducing the film forming property, even if it can be formed, there is a difference in light diffusivity and transmittance depending on the location, As a result, luminance unevenness may occur when mounted on a surface light source. When an incompatible resin is used as the diffusing element (D), uniform light diffusibility and transparency can be obtained by controlling the dispersion diameter at the time of kneading with a biaxial stretching machine within the above range.

  Moreover, when the light-diffusion film of this invention is a laminated film, the thermoplastic resin (sufficient vacuum drying was performed as needed using the composite film forming apparatus which has a subextruder other than the said main extruder. For example, a resin layer (for S layer) raw resin or a mixture of chips and various additives when a light diffusion layer (D layer) is formed by a coextrusion method and a mixture of various additives is heated to be sub-extruded. Co-extrusion lamination by feeding to the machine.

  Further, in the case of melt extrusion, it is preferable to obtain a molten sheet (in the case of a laminated film, a molten laminated sheet) by filtering through a filter having a mesh of 40 μm or less and introducing it into a T die die. This molten sheet is closely cooled and solidified by static electricity on a drum cooled to a surface temperature of 10 ° C. or higher and Tg−15 ° C. of the matrix resin to produce an unoriented (unstretched) film. The unoriented film is led to a group of rolls heated to a temperature of Tg ° C. or more and Tg + 50 ° C. or less, and doubled by stretching between the rolls in the longitudinal direction (that is, the traveling direction of the film, hereinafter sometimes referred to as “longitudinal direction”). The film is stretched 4 times or less and cooled with a roll group having a temperature of 20 ° C. or more and Tg ° C. or less of the matrix resin to obtain a uniaxially oriented (uniaxially stretched) film (this stretching process is sometimes referred to as a longitudinal stretching process). ).

  Subsequently, the both ends of the uniaxially oriented film are guided to a tenter while being gripped by clips, and in an atmosphere heated to a temperature of Tg + 5 ° C. to Tg + 70 ° C. of the matrix resin, the direction perpendicular to the longitudinal direction (that is, the film width direction is set) (Hereinafter sometimes referred to as the “lateral direction”) to obtain a biaxially oriented (biaxially stretched) film by pulling to 2 times or more and 4 times or less (this stretching process is sometimes referred to as a lateral stretching process). ). By this series of stretching steps, when flat inorganic particles and / or crosslinkable resin particles are used as the raw material for the diffusion element (D), the flat particles can be arranged in parallel with the film surface. It can be formed as (d1). Further, when an incompatible resin is used as the raw material for the diffusion element (D), it is co-stretched with the resin serving as the matrix, becomes a flat shape, and can be formed as the diffusion element (d1).

  The stretching ratio in the longitudinal direction and the width direction is preferably 2.2 to 4 times, more preferably 2.5 to 3.5 times, and still more preferably 2.8 to 3.3 times. It is as follows. If the draw ratio exceeds 4 times, film breakage is likely to occur in the drawing process, or even if the film can be formed, peeling occurs at the interface between the matrix of the internal diffusion layer (ID layer) and the diffusion element (D), and bubbles are generated. As a result, the light transmittance may decrease. Further, if the draw ratio is less than 2.0 times, the mechanical strength of the film is lowered or the formation of the diffusing element (d1) is insufficient, and the obtained film is in the vicinity of the direction perpendicular to the incident direction. In some cases, the light λ3 scattered in the light increases and the luminance decreases. In the light diffusing film of the present invention, by setting the draw ratio to 2.2 times or more and 4 times or less, it is possible to efficiently produce uneven brightness when incorporated into a surface light source without reducing the film forming property and the mechanical strength of the film. It can be set as the light-diffusion film which can be compatible with elimination and high brightness.

  Further, if necessary, in order to complete the crystal orientation of the obtained biaxially oriented film and to impart flatness and dimensional stability, it is continuously Tg + 70 ° C. or higher in the tenter, an internal diffusion layer (ID layer). The melting point Tm of the resin used as the matrix is 1-10 ° C. or lower (150 ° C. or higher and 240 ° C. or lower when the matrix resin is polyethylene terephthalate). Then, if necessary, a corona discharge treatment or the like may be performed to further improve the adhesion to other materials. During the heat treatment step, a relaxation treatment of 0.1 to 12% may be performed in the width direction or the longitudinal direction as necessary.

  In general, the higher the heat treatment temperature, the higher the thermal dimensional stability, and the flatness of the diffusing element (d1) tends to increase. Therefore, the film of the present invention has a high temperature (180 ° C. or higher) in the film forming process. It is preferable to heat-treat. More preferably, when the diffusing element (D) is made of a thermoplastic resin, it is preferably heat-treated at a melting point or higher when the resin is a crystalline resin, or at a glass transition temperature or higher when the resin is an amorphous resin. Thereby, not only can the flatness of the diffusion element (d1) be increased, but also the bubbles generated slightly during stretching can be eliminated, and the volume occupancy of the bubbles in the internal diffusion layer (ID layer) can be reduced. High transmittance can be obtained.

  In addition, the light diffusion film of the present invention has a laminated structure, and in order to develop moldability in the laminated resin layer S, the melting point Tm2 or more of the resin constituting the resin layer (S layer), the internal diffusion layer ( As a result of melting the resin layer (S layer) during the heat treatment step and eliminating the orientation due to stretching by heat treatment in the range of the melting point Tm1-10 ° C. or less of the resin serving as the matrix of the ID layer) Is preferable. By winding up such a biaxially oriented film, the light diffusion film of the present invention can be obtained. When biaxial stretching is performed, either sequential stretching or simultaneous biaxial stretching may be used. However, when the simultaneous biaxial stretching method is used, film breakage in the manufacturing process can be prevented, and adhesion to the heating roll can be achieved. The transfer defects caused by this are unlikely to occur. Further, after biaxial stretching, the film may be re-stretched in the longitudinal direction and / or the width direction. In addition, various additives may be added to the light diffusion film of the present invention as long as the effects of the present invention are not lost.

  In the light diffusing film of the present invention, the method for forming the light diffusing layer (D layer) is, for example, a method in which a coating material containing particles is applied to the surface of the film serving as a substrate (coating method). A method in which the raw material of the light diffusing layer is put into an extruder and melt-extruded and laminated while extruding from the die (coextrusion method) on the film as the base material (co-extrusion method). Etc. by thermocompression bonding with the base material 1 by the method (thermal laminating method), by laminating with the film as the base material through an adhesive (adhesion method), sandblasting method, thermal imprinting method or optical imprinting method. Examples thereof include a method of providing an uneven shape and a method of combining these. In addition, when the light diffusion layer (D layer) has an anisotropic shape, in addition to the above-described thermal imprinting method and optical imprinting method, while controlling the direction of the particles on the film surface with a coating agent containing rod-like particles Examples thereof include a method of coating, a method of providing irregularities on the surface by hairline processing (processing for scratching the film surface), and the like. The sand blasting method is a method in which light diffusibility is expressed by spraying fine gold and sand on the surface of a film to give fine scratches. In addition, the hairline processing and the surface of the base material are rubbed with a brush or the like to form linear scratches.

  Examples of the coating method used for the coating method include multi-roll coating, blade coating, wire bar coating, slit die coating, gravure coating, knife coating, reverse roll coating, spray coating, offset gravure coating, and spin coating. . In addition, the thermal imprint method is a method in which a mold with a fine surface shape and a moldable resin layer (S layer) are heated, the mold is pressed against the film, cooled, and then released. In this method, the shape applied to the mold surface is transferred to the film surface. Here, the resin used for thermal imprinting may be a thermoplastic resin or a thermosetting resin, but a highly transparent resin is preferable. On the other hand, the photoimprint method is a state in which a photocurable resin layer is coated with a photocurable resin and then pressed with a mold having a fine surface shape on the photocurable resin layer, or photocurable on the mold. After applying the resin, with the film overlaid, light such as ultraviolet rays is irradiated from the mold side or film side, the photocurable resin is cured, and then the mold is released to form the shape applied to the mold surface. This is a technique for transferring to resin. When transferring by heating and pressing, first, the film of the present invention in which a resin layer (S layer) having moldability is laminated, and a mold are made to have a glass transition temperature Tg2 or higher and lower than the melting point Tm of the resin layer (S layer). Heat within the temperature range. Next, the film of the present invention and the mold are brought close to each other, pressed as it is at a predetermined pressure, and held for a predetermined time. Next, the temperature is lowered while maintaining the pressed state, and finally the pressure is released to release the sheet from the mold.

  In the case of mold forming using heating and pressurization, the heating temperature and the press temperature (T1) are Tg2 or more (Tg2 + 60 ° C.) or less (however, the melting point Tm1 or less of the resin serving as the matrix of the internal diffusion layer (ID layer)) ) Is preferable. If the heating temperature and the pressing temperature (T1) are less than Tg2, the resin layer (S layer) on the surface is not sufficiently softened, so that deformation when pressing the mold is difficult to occur, and pressure required for molding Becomes very high. If the temperature exceeds Tg2 + 60 ° C., the heating temperature and the press temperature T1 are high and inefficient in energy, and the difference in volume variation during heating / cooling of the mold and the sheet becomes too large. Even if the mold cannot be released due to being bitten into the mold, the accuracy of the transferred pattern is lowered or the pattern is partially lost, which is not preferable. By setting the heating temperature and the press temperature (T1) to Tg2 or more (Tg2 + 60 ° C.), it is possible to achieve both good moldability and releasability.

  Further, in the case of mold forming using heating and pressurization, the pressing pressure is appropriately adjusted depending on the elastic modulus value of the resin layer (S layer) on the surface at the pressing temperature T1, but preferably 0. It is from 5 MPa to 50 MPa, more preferably from 1 MPa to 30 MPa. If the pressing pressure is less than 0.5 MPa, the resin is insufficiently filled in the mold and the pattern accuracy is lowered. On the other hand, if it exceeds 50 MPa, the required load increases, the load on the mold increases, and the repeated use durability decreases, which is not preferable. By setting the press pressure to 0.5 MPa or more and 50 MPa or less, good transferability can be obtained.

  Further, in the case of mold forming using heating and pressurization, the press pressure holding time is appropriately adjusted according to the elastic modulus value of the resin layer (S layer) at the press temperature T1 and the molding pressure. In the case of a flat plate press, it is preferably 10 seconds or longer and 10 minutes or shorter. If the press pressure holding time is less than 10 seconds, the resin is insufficiently filled in the mold, and the pattern accuracy is lowered or the in-plane uniformity is lowered. On the other hand, if it exceeds 10 minutes, deterioration due to thermal decomposition of the resin may occur and the mechanical strength of the molded product may be lowered, which is not preferable. When the press pressure holding time is 10 seconds or more and 10 minutes or less, both good transferability and mechanical strength of the molded product can be achieved. However, in the case of roll-to-roll molding, the press time may be 10 seconds or less.

  In addition, in the case of mold forming using heating and pressurization, the press pressure release temperature T2 is preferably lower than the press temperature T1 within a temperature range of (Tg2-10 ° C.) to (Tg2 + 30 ° C.). More preferably, it is (Tg2-10 ° C) or more and (Tg2 + 30 ° C) or less. If the press pressure release temperature T2 is less than Tg2-10 ° C., the deformation of the resin during pressing remains as a residual stress, and even if the pattern collapses or can be released during mold release, the thermal stability of the molded product Is unfavorable because of lowering. On the other hand, if it exceeds Tg2 + 30 ° C., the flowability of the resin at the time of pressure release is high, so that the pattern is deformed and the transfer accuracy is lowered. By setting the press pressure release temperature T2 to (Tg2-10 ° C.) or more and (Tg2 + 30 ° C.) or less, it is possible to achieve both good transferability and releasability. In the case of mold forming using heating and pressurization, the mold release temperature T3 is preferably in the temperature range of 20 ° C. or higher and T2 ° C. or lower, more preferably in the temperature range of 20 ° C. or higher and Tg 2 ° C. or lower. It is. If the mold release temperature exceeds T2 ° C, the fluidity of the resin at the time of mold release is high, or the surface is softened and has adhesiveness, and the pattern is deformed at the time of mold release and the accuracy is lowered. This is not preferable. By setting the temperature at the time of mold release to 20 ° C. or higher and T2 ° C. or lower, the mold can be released with high pattern accuracy.

In addition, when transferring using electromagnetic wave irradiation, first, the film of the present invention in which a resin layer having a moldability (S layer) is laminated, and a mold having unevenness reversed from the pattern to be transferred are brought close to each other, After pressing at a predetermined pressure as it is, the resin is cured by irradiating electromagnetic waves from either the mold side or the film side of the present invention. Next, the press pressure is released to release the film from the mold. When transferring using electromagnetic wave irradiation, the press pressure depends on the viscosity of the material to be shaped at the shaping temperature, but is preferably 0.05 MPa or more and 10 MPa or less, more preferably 0.1 MPa or more and 5 MPa or less. is there. If the pressing pressure is less than 0.05 MPa, the resin is insufficiently filled in the mold and the pattern accuracy is lowered. On the other hand, if it exceeds 10 MPa, the required load increases, the load on the mold increases, and the repeated use durability decreases, which is not preferable. By setting the pressing pressure within this range, good transferability can be obtained. In the case of transcription using electromagnetic irradiation, irradiation of electromagnetic wave is dependent on such extinction at a wavelength of cumulative energy irradiation is 10 mJ / cm ² or more 5000 mJ / cm ² or less. If the irradiation amount of electromagnetic waves is less than 10 mJ / cm ² , the resin will not be cured sufficiently and the pattern accuracy will be reduced, or the strength will be insufficient at the time of mold release, and it will break due to mold release stress. Sexuality decreases. ^{On the other hand} , if it exceeds 5000 mJ / cm ² , it is not preferable because it may be cured too much and curl may occur due to curing shrinkage. By setting the irradiation amount of electromagnetic waves within this range, both good transferability and mechanical strength of the molded product can be achieved. When transferring using electromagnetic wave irradiation, the temperature during the series of steps is not particularly limited, but the press temperature is 10 ° C. or higher and 200 ° C. or lower, more preferably 10 ° C. or higher and 150 ° C. or lower, and most preferably 10 ° C. or higher and 100 ° C. or lower. It is below ℃. When the press temperature is higher than 200 ° C., the fluidity of the resin becomes too high, and the resin flows before pressing, or the resin is cured before pressing, and the molding becomes insufficient. Moreover, mold release temperature T3 has good glass transition temperature Tg3 or less of hardened | cured material, More preferably, it is Tg3-10 degrees C or less, Most preferably, it is Tg3-20 degrees C or less. If the mold release temperature T3 exceeds Tg3 ° C., the flowability of the resin at the time of mold release is high, or the surface is softened and has adhesiveness, and the pattern is deformed at the time of mold release and the accuracy is lowered. This is not preferable because there are some cases. By setting the temperature at the time of mold release to Tg3 or less, the mold can be released with high pattern accuracy. In the case of transferring using electromagnetic wave irradiation, the degree of cure can be further improved by subjecting the film obtained by mold shaping to a heat treatment. As the method, at least one of the mold and the film is heated at the time of pressing the above-mentioned mold, the method of heating at least one of the mold and the film after the release after curing by electromagnetic wave irradiation, and the heat treatment after the pattern forming step. Any of the above methods is preferably used. Among them, the method of heating at least one of the mold temperature T1 at the time of mold pressing or the temperature T2 of the laminated body 1 is preferably performed because the number of steps can be reduced. Further, in order to further increase the degree of curing, these may be combined.

  Examples of the transfer method include the above-mentioned methods, but in addition to a method of pressing a lithographic plate (lithographic pressing method), a roll-shaped mold having irregularities formed on the surface is used to form a roll-shaped sheet. It may be a roll-to-roll continuous molding to obtain a molded body. Roll-to-roll continuous forming is superior to the lithographic press method in terms of productivity.

  The light diffusing film of the present invention has the above-described configuration and production method. By using this film, high unevenness extinction is exhibited regardless of which part of the plurality of optical film groups 40 in FIG. 4 is used. Among them, it is used as the optical film 41 directly above the diffusion plate in FIG. 4 in that the high brightness and high unevenness elimination effect are expressed, in that the backscattered light can be effectively used and the brightness can be increased. More preferred.

  Since the light diffusing film of the present invention has a flat diffusing element, the light diffusing film itself has high brightness and high unevenness erasing property. ) Is also a preferred form. In the case where the light diffusion layer (D layer) is provided, it is preferably installed so that the surface on which the light diffusion layer (D layer) is not formed faces the diffusion plate 30 when mounted on the surface light source. With such a configuration, it is possible to control the emission direction of the light diffused in the internal diffusion layer (ID layer) with the light diffusion layer (D layer). As a result, an excellent surface light source with higher luminance and uniformity can be obtained. In addition, when a light diffusion layer (D layer) is formed on both side surfaces, either surface may be disposed to face the diffusion plate 30.

  In the surface light source using the light diffusion film of the present invention, it is preferable to mount an optical film having another function on the above film as long as the effect of the light diffusion film of the present invention is not lost. By using another optical film, it is possible to further increase the luminance of the surface light source using the light diffusion film of the present invention and the luminance uniformity. The installation place of another optical film may be between the diffusion plate 30 and the light diffusion film of the present invention (that is, in FIG. 4, the light diffusion film of the present invention is 42 and the other film is 41), Other films may be stacked on the light diffusing film of the present invention (that is, in FIG. 4, the light diffusing film of the present invention is 41 and another film is stacked with 42, 43...). As a result, the quality as a surface light source can be improved. Examples of another optical film include a prism sheet, a diffusion sheet having isotropic diffusibility, an anisotropic diffusive sheet, and a polarization separation film.

  The surface light source using the light diffusing film of the present invention is superior to conventional direct surface light sources in terms of excellent light utilization efficiency, high brightness, and wide viewing angle, and various display media such as TVs, monitors, etc. It can use suitably for the use which irradiates a liquid crystal display element from a back surface, such as.

(Measuring method)
A. Cross-section observation For the master batch, unstretched film, final film, and product film prepared in each Example / Comparative Example, a cross-section was cut out using a microtome, and platinum-palladium was deposited, and then JEOL Ltd. A 3000-5000 times photograph was taken with a field emission scanning electron microscope “JSM-6700F”. The details are as follows. From the obtained image, the volume average particle diameter of the master batch, the volume average particle diameter of the unstretched film, the flatness, the number of diffusing elements in the film thickness direction, the volume average particle diameter, the diffusing elements. The volume occupancy of (D) and the volume occupancy of bubbles were determined.
A-1. Method for obtaining flatness (A1) Using a microtome, an observation sample in the form of a thin film slice is produced without crushing the cross section of the film in the thickness direction.
(A2) An image obtained by magnifying the obtained section 5000 times using a transmission electron microscope (TEM) (transmission electron microscope “H-7100FA” manufactured by Hitachi, Ltd.) is obtained. The observation location is determined randomly within the internal diffusion layer (ID layer). Further, when it is difficult to identify the diffusing element in the image, the film is dyed in advance using osmium acid, ruthenium oxide or the like as appropriate. Note that the thickness direction of the film and the vertical direction of the image are made to coincide. If the diffusion element (D) does not fully enter at a magnification of 5000 times, images obtained by shifting the observation positions are obtained and joined together without any gaps to obtain an observation image.
(A3) The short axis length and the long axis length are obtained for one diffusion element (D) in the internal diffusion layer (ID layer) in the image. Hereinafter, a description will be given with reference to FIGS. 1-3, the long axis length of the diffusing element 1 is the other end from one end (the leftmost end of the diffusing element in the direction parallel to the film surface direction) 2 in the direction parallel to the film surface direction. This is the length of the line segment 4 when the line segment 4 is connected to (the rightmost end of the diffusing element in the direction parallel to the film surface direction) 3. Here, the line segment 4 is not necessarily parallel to the film surface direction (see FIGS. 2 and 3). The short axis length is a line segment 8 from one end (upper end) 6 to the other end (lower end) 7 of the diffusing element passing through the middle point 5 of the line segment 4 and perpendicular to the line segment 4. This is the length of the line segment 8 when tied. Here, the line segment 8 does not necessarily include the midpoint 5 (see FIG. 3).
(A4) A value obtained by dividing the major axis length by the minor axis length (major axis length / minor axis length) is defined as the flatness of the diffusion element (D).
(A5) The flatness of other diffusion elements in the internal diffusion layer (ID layer) in the image is also determined by the methods (A1) to (A4), and is included in the internal diffusion layer (ID layer). The ratio of the number of diffusion elements (d1) to the total number of diffusion elements (D) is obtained.
(A6) The film cutting place was randomly changed and the same procedure as (A1) to (A5) was performed 100 times in total, and the diffusion element (D) contained in the internal diffusion layer (ID layer) with the average value The ratio of the number of diffusion elements (d1) to the total number of.
A-2. Obtaining the number of diffusing elements in the film thickness direction (B1) Using a microtome, an observation sample in the form of a thin film slice is produced without crushing the film cross section in the thickness direction.
(B2) An image obtained by magnifying the obtained section 2000 times using a transmission electron microscope (TEM) (transmission electron microscope “H-7100FA” manufactured by Hitachi, Ltd.) is obtained. The observation location is determined randomly within the internal diffusion layer (ID layer). Further, when it is difficult to determine the diffusing element (D) in the image, the film is dyed in advance using osmium acid, ruthenium oxide or the like as appropriate. Note that the thickness direction of the film and the vertical direction of the image are made to coincide. In addition, when the entire film thickness does not enter at 2000 times, an image in which the observation position is shifted in the thickness direction is obtained, and the images are joined together without gaps to obtain an observation image in which the entire film thickness enters.
(B3) A line perpendicular to the surface direction of the film (line in the film thickness direction) is drawn over the entire film thickness at an arbitrary location in the image, and the number of diffusion elements (D) intersecting with the line is counted.
(B4) For the other 10 locations in the image, the number of diffusion elements (D) in the film thickness direction is counted in the same manner as in (B3) above, and with the average value, the number of diffusion elements in the film thickness direction in the image (B5) The film cutting place is randomly changed, and the same procedure as (B1) to (B4) is performed 20 times in total, and the average value is taken as the number of diffusion elements in the film thickness direction.
A-3. In-plane long-axis length, in-plane single-axis length, in-plane long-axis length to in-plane short-axis length ratio (in-plane long-axis length / in-plane short-axis length) (C1) microtome The film is cut in parallel to the film surface direction without crushing the film cross section in the surface direction.
(C2) Next, the cut section is observed using an electron microscope, and an image magnified 5000 times is obtained. The observation location is determined randomly within the internal diffusion layer (ID layer), but the vertical direction of the image is parallel to the longitudinal direction of the film and the horizontal direction of the image is parallel to the film width direction. Shall. In addition, when it is difficult to identify the diffusing element of the diffusing element (D) in the image, the film may be dyed in advance using osmium acid or the like as appropriate.
(C3) The in-plane short axis length and the in-plane long axis length are obtained for one diffusion element (D) in the internal diffusion layer (ID layer) in the image.
Hereinafter, a description will be given with reference to FIGS. 11 to 13, the in-plane long axis length of the diffusing element (D) is from one end of the diffusing element in the direction parallel to the film longitudinal direction (the leftmost end of the diffusing element in the direction parallel to the film surface direction) 2 '. This is the length of the line segment 4 ′ when connecting to the other end (the rightmost end of the diffusing element in the direction parallel to the film longitudinal direction) 3 ′ with the line segment 4 ′. Here, the line segment 4 ′ is not necessarily parallel to the film longitudinal direction (see FIGS. 12 and 13). Further, the in-plane short axis length means that one end (upper end) 6 ′ of the diffusing element (D) passes through the midpoint 5 ′ of the line segment 4 ′ and is perpendicular to the line segment 4 ′ to the other end ( This is the length of the line segment 8 when connecting the lower end 7 ′ to the line segment 8 ′. Here, the line segment 8 ′ does not necessarily include the midpoint 5 ′ (see FIG. 13).
(C4) A value obtained by dividing the in-plane long axis length by the in-plane short axis length (in-plane long axis length / in-plane short axis length), the in-plane long axis length and in-plane short axis of the diffusion element The length ratio (in-plane long axis length / in-plane short axis length) is used.
(C5) Similarly for the other diffusion elements (D) in the internal diffusion layer (ID layer) in the image, the ratio of the in-plane long axis length to the in-plane short axis length (in-plane long axis length / in-plane Find the short axis length). However, the measurement target is limited to a case where the entire diffusion element (D) is within the image.
(C6) The film cutting place is randomly changed and the same procedure as (C1) to (C5) is performed 100 times in total.
(C7) Using the numerical value of the ratio of the in-plane long axis length to the in-plane short axis length (in-plane long axis length / in-plane short axis direction length) of all diffusing elements obtained by the above procedure. Then, the arithmetic average value is obtained, and the arithmetic average value is obtained by comparing the in-plane long axis length and the in-plane short axis length of the diffusion element (D) in the internal diffusion layer (ID layer) (in-plane length). Axis length / in-plane minor axis length). Similarly, the arithmetic average value of the numerical values of the in-plane minor axis length and the in-plane major axis length of the diffusion element (D) obtained by the above procedure is obtained, and the arithmetic average value is averaged. In-plane minor axis length, average in-plane major axis length.
A-4. Determining the Volume Occupancy of the Diffusing Element (D) (D1) The area of the internal diffusion layer (ID layer) in the image obtained in (A2) is measured, and this is designated as A.
(D2) The areas of all diffusion elements (D) existing in the internal diffusion layer (ID) in the image are measured, and the total area is defined as B. Here, the measurement target is not limited to the entire diffusion element (D) within the image, but includes the diffusion element (D) in which only a part of the diffusion element (D) appears in the image.
(D3) Divide B by A (B / A) and multiply it by 100 to calculate the volume occupancy (%).
(D4) The same measurement / calculation was performed for a total of 100 images obtained from (A6), and the arithmetic mean value of volume occupancy (%) obtained for each image was obtained. The value is defined as the volume occupancy (%) of the diffusion element (D) in the internal diffusion layer (ID layer).
A-5. Method for obtaining bubble volume occupancy (E1) The area of the internal diffusion layer (ID layer) in the image obtained in (A2) above is measured, and this is designated as A.
(E2) The area of all the bubbles existing in the internal diffusion layer (ID layer) in the image is measured, and the total area is defined as B. Here, the measurement target is not limited to the bubbles that are entirely contained in the image, but includes bubbles that are only partially displayed in the image.
(E3) By dividing B by A (B / A) and multiplying it by 100, the volume occupancy (%) of bubbles in the internal diffusion layer (ID layer) is calculated.
(E4) The same measurement and calculation are performed for the total of 100 images obtained from (A6), and the arithmetic mean value of the volume occupancy (%) of the bubbles obtained from each image is obtained. The arithmetic average value is defined as the volume occupancy rate of bubbles in the internal diffusion layer (ID layer).
A-6. Using the volume average particle size of the master batch and the volume average particle size (G1) microtome of the unstretched film, parallel to the film surface direction without crushing the cross section in the TD direction (lateral direction) and the parallel direction. Disconnect.
(G2) For each resin particle observed in the cross section in the image, the cross-sectional area S is obtained. The particle diameter d obtained by the following formula (1) is obtained. D = 2 × (S / π) ^{1 /} 2 (1)
(Where π is the circumference)
(G3) Moreover, Dv was calculated | required in following formula (4).
Dv = Σ [4 / 3π × (d / 2) ³ × d] / Σ [4 / 3π × (d / 2) ³ ] (4)
(Where π is the circumference)
(G4) The above G1) to G2) are carried out at 10 locations, and the volume average particle diameter Dv is determined by the average value. Note that the above evaluation is performed in an area of 2500 μm ² or more per observation point.

B. Glass transition temperature, melting point, crystallization enthalpy, crystal melting calorie According to JIS K7122 (1999), the differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. The measurement was carried out using / 5200 "and determined by the following procedures (F1) to (F4).
(F1) The sample sealed in the sample pan is heated at a temperature increase rate of 20 ° C./min from a temperature of 25 ° C. to 300 ° C. at a temperature increase rate of 20 ° C./min (1stRUN).
(F2) Hold in that state for 5 minutes, and then rapidly cool to 25 ° C. or lower.
(F3) The temperature is raised again from room temperature to 300 ° C. at a temperature raising rate of 20 ° C./min (2ndRUN).
(F4) In the obtained 2ndRUN differential scanning calorimetry chart, in the stepwise change portion of the glass transition, a straight line equidistant in the vertical axis direction from the extended straight line of each base line and the stepwise change of the glass transition The glass transition temperature Tg is the point where the curve of the portion intersects. Further, the melting point of the resin is determined by the temperature at the peak top in the crystal melting peak of 2ndRun. Further, the area of the exothermic peak accompanying crystallization is the crystallization enthalpy ΔHcc, and the area of the endothermic peak accompanying melting is the crystal melting heat quantity ΔHm. Refractive Index The refractive index Nm of the matrix resin and the refractive index Nd of the diffusing element (d1) were each measured using an Abbe refractometer with a single film sheet and a sodium D line (wavelength 589 nm) as a light source. Hereinafter, an example of a method for manufacturing a single film sheet will be described.

  The film is dissolved in hexafluoroisopropanol to dissolve the matrix resin. Next, the diffusion element (d1) that did not dissolve in the solution is separated, and the solvent is dried to obtain the matrix resin and the diffusion element (d1), respectively. This is formed into a sheet shape by a known method to produce a single film sheet, and the refractive index of the sheet is measured.

D. Light transmittance and haze haze meter NDH-5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the total light transmittance and haze in the film thickness direction, which were the light transmittance and haze of the film, respectively. In addition, about the case where light is incident from each surface, the measurement is carried out at any 10 points in the film, and the transmittance is determined by the higher value of the average value of each transmittance. The average value of haze was taken as haze.

E. Appearance (Appearance of light diffusion layer when light diffusion layer is formed by application)
The film on which the light diffusing layer was formed was observed with naked eyes of reflected light under a fluorescent lamp to confirm the repelling part, and the part was painted with oily magic. Next, the area of the filled portion was determined, and the area ratio (%) of the filled portion with respect to the total area of the film was determined.
S when the area ratio of the obtained part is 1% or less,
A is greater than 1% and less than 1.5%,
B if 1.5% and less than 2.0%
The case of 2% or more was defined as C.
S or A or B is good, and S is the best.

F. Formability (Appearance of light diffusion layer when light diffusion layer is formed by mold forming)
After cutting out the cross section of the film on which the mold and the light diffusion layer (D layer) were formed, and depositing platinum-palladium as necessary, a field emission scanning electron microscope “JSM-6700F” manufactured by JEOL Ltd. was used. Then, the photograph was taken at 300 to 5000 times, the cross-section was observed, and the depth H of the mold concave portion and the height H ′ of the convex portion of the light diffusion film were obtained with images of the same magnification, respectively. The average value was defined as the depth H of the mold recess and the height H ′ of the projection of the light diffusion film.

Formability was determined as follows. A when the ratio H ′ / H of the convex portion height H ′ of the light diffusion layer (D layer) of the light diffusion film and the depth H of the mold concave portion is 0.9 or more, A,
B is 0.8% or more and less than 0.9%.
The case of less than 0.8% was defined as C.
A or B is good, and A is the best.

G. Luminance, display quality 20-inch size direct light source (surface light source consists of a case, CCFL, diffuser and reflector. Also, the number of CCFLs is 16, CCFL diameter is 3mm, CCFL The distance between the diffuser and the CCFL is 1 cm, the reflector is E6ZV (manufactured by Toray Industries, Inc.) with a thickness of 300 μm, and the diffuser is RM401 (manufactured by Sumitomo Chemical Co., Ltd.). The film produced in the examples and comparative examples was placed on the upper side of the diffusion plate, and two light diffusion films TDF187 (manufactured by Toray Sehan) were stacked thereon (Configuration A). Next, a voltage of 12 V was applied to light the CCFL, and the surface light source was activated. After 50 minutes, using EYESCALE-3 (Eye System Co., Ltd.), the attached CCD camera was installed at a point 90 cm from the surface light source surface so as to be in front of the surface light source surface, and luminance (cd / m) ² ) was measured. Next, the CCD camera was tilted by 45 ° in the direction perpendicular to the longitudinal direction of the CCFL, centering on the center of the outermost surface of the surface light source, and the luminance L45 (cd / m ² ) at that time was measured. Note that the luminance passes through the central portion of the surface light source, and on the line perpendicular to the longitudinal direction of the CCFL, the luminance at the positions of the eight CCFLs (a total of eight points) and the midpoint of these eight CCFLs The luminance values at the positions (total 7 points) were extracted, the average luminance value at the CCFL position was Lmax, and the average luminance value at the midpoint position of the total CCFL was Lmin. In the same way for the luminance in the 45 ° direction, the average value of luminance at the CCFL position was L45max, and the average value of luminance at the midpoint position of the total CCFL was L45min. Using the obtained Lmax, Lmin, L45max, and L45min, the average luminance Lave was obtained by the following equation (1), the luminance unevenness ΔL in the front direction was obtained by the following equation (2), and the luminance unevenness ΔL45 was obtained by the following equation (3). .

Average luminance Lave = (Lmax + Lmin) / 2 (1)
Frontal luminance unevenness ΔL = Lmax−Lmin (2)
45 ° direction luminance unevenness ΔL45 = L45max−L45min (3)
When the light diffusion layer is formed, the surface on which the light diffusion layer is not formed is opposed to the diffusion plate (Configuration I) and the surface on which the light diffusion layer is formed is opposed. In each case (Configuration II), the measurement was performed. Subsequently, the order of the film of the present invention and one diffusion film was changed (Configuration B), and similarly, average luminance Lave, luminance variation ΔL in the front direction, and luminance variation ΔL45 in the 45 ° direction were obtained.

Average brightness Lave is
8600cd / ^{m 2} or more when S,
In the case of 8400 cd / m ² or more and less than 8600 cd / m ² A,
In the case of 8200 cd / m ² or more and less than 8400 cd / m ² B,
In the case of 8000 cd / m ² or more and 8200 cd / m ² or less C,
8000 cd / m ² or less D,
It was.
S or A or B or C is good, and S is the best.

Further, the luminance unevenness ΔL in the front direction is
When 100 cd / m ² or less S,
Greater than 100cd / ^{m 2} 125cd / ^{m 2} or less in the case A,
Greater than 125cd / ^{m 2} 150cd / ^{m 2} or less in the case B,
If greater than 150 cd / m ² C,
It was.
S or A or B is good, and S is the best.
Further, 45 ° direction of uneven brightness ΔL45 is 100 cd / ^{m 2} or less in the case S,
Greater than 100cd / ^{m 2} 125cd / ^{m 2} or less in the case A,
Greater than 125cd / ^{m 2} 150cd / ^{m 2} or less in the case B,
If greater than 150 cd / m ² C,
It was.
S or A or B is good, and S is the best.
In addition, the display quality does not confirm moire when the screen is observed with the naked eye.
Moire is confirmed B
It was. A is good.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention concretely, this invention is not limited to this.

(material)
・ Polyester resin (A)
A-1 (PET): Using terephthalic acid as the dicarboxylic acid component, using ethylene glycol as the diol component, and adding 300 ppm in terms of antimony atoms to the polyester pellets from which antimony trioxide (polymerization catalyst) is obtained, A polycondensation reaction was performed to obtain polyethylene terephthalate (PET) pellets having a glass transition temperature of 80 ° C. and a melting point of 255 ° C.
A-2 (Naphthalenedicarboxylic acid copolymerized PET): Polyester capable of obtaining antimony trioxide (polymerization catalyst) using 85 mol% terephthalic acid as a dicarboxylic acid component, 15 mol% 2,6-naphthalenedicarboxylic acid and ethylene glycol as a diol component. It added so that it might become 300 ppm in conversion of an antimony atom with respect to a pellet, the polycondensation reaction was performed, and the naphthalene copolymerization PET pellet of glass transition temperature 95 degreeC and melting | fusing point 225 degreeC was obtained.

Unmodified incompatible resin b1-1 (PMP): TPX “DX820” (manufactured by Mitsui Chemicals, MFR 180 g / 10 min, 80 ° C. dynamic storage elastic modulus 140 MPa, melting point 235 ° C.) was used.
b1-2 (PMP): TPX “RT-18” (manufactured by Mitsui Chemicals, MFR 26 g / 10 min, 80 ° C. dynamic storage elastic modulus 140 MPa, melting point 235 ° C.) was used.
b1-3 (PMP): TPX “DX310” (Mitsui Chemicals, MFR 100 g / 10 min,
80 ° C. dynamic storage elastic modulus 80 MPa, melting point 225 ° C.).
b1-4 (flexible PMP): TPX “T3725” (manufactured by Mitsui Chemicals, Inc., manufactured by Mitsui Chemicals, MFR 25 g / 10 min, 80 ° C. dynamic storage elastic modulus 20 MPa, melting point 225 ° C.) was used.
b1-5 (flexible PMP): TPX “T3733” (manufactured by Mitsui Chemicals, Inc., manufactured by Mitsui Chemicals, MFR 150 g / 10 min, 80 ° C. dynamic storage elastic modulus 20 MPa, melting point 225 ° C.) was used.
b1-6 (polypropylene (homo)): Prime Polypro “F-704NP” (manufactured by Prime Polymer Co., Ltd., MFR 7 g / 10 min, 80 ° C. dynamic storage elastic modulus 200 MPa, melting point 165 ° C.) was used.
b1-7 (polyethylene): Novatic “HF560” (manufactured by Nippon Polyethylene Co., Ltd., MFR 7 g / 10 min, 80 ° C. dynamic storage elastic modulus 180 MPa, melting point 124 ° C.) was used.
B1-8 (polystyrene) using: GPPS “G430 (manufactured by Nippon Polystyrene Co., Ltd., MFR 7 g / 10 min, 80 ° C. dynamic storage elastic modulus 300 MPa).

Modified incompatible resin b2-1 (maleic anhydride-modified PMP): TPX “MM-101B” (manufactured by Mitsui Chemicals, Inc., acid value 6 KOH mg / g) was used.
b2-2 (maleic anhydride-modified polypropylene): Umex “1001” (manufactured by Sanyo Chemical Industries, Ltd., acid value: 26 KOH mg / g) was used.
b2-3 (maleic anhydride-modified polyethylene): Umex “2000” Admer (manufactured by Mitsui Chemicals, Inc., acid value 30) was used.
b2-4 (epoxy-modified polystyrene): “Epofriend” AT501 (manufactured by Daicel Chemical Industries, Ltd., oxirane oxygen concentration 1.5 wt%) was used.

Example 1
The raw material mixture shown in Table 1 was supplied to a twin-screw extruder equipped with a vacuum vent, melted and kneaded at a temperature of 250 ° C, extruded into water at 60 ° C in a gut shape from a die, and rapidly cooled to form a strand. Next, this was cut to obtain a master chip in which PMP was dispersed in PET. When the cross section of the obtained chip was observed, it was found that PMP was dispersed with a volume average particle size of 2.0 μm. Then, the master batch obtained and PET (A-1) mixed so as to have the composition shown in Table 2 were vacuum-dried at a temperature of 180 ° C. for 2 hours and then supplied to a single screw extruder. After melt extrusion at a temperature of 280 ° C., the mixture was filtered through a 30 μm cut filter and then introduced into a T die die. Further, a sub-extruder was used separately from the main extruder, and PET (melting point TA: 255 ° C.) pellets were supplied to this sub-extruder. Next, the component layers supplied to the sub-extruder are in a thickness ratio on both surface layers of the component layer supplied to the main extruder, and the sub-extruder component layer: main extruder component layer: sub-extruder component layer = 1: 8. : 1, that is, the ID layer thickness / the thickness of the layers other than the ID layer (S layer) is combined to be 4/1, and melted three-layer lamination co-extrusion is performed from the inside of the T die die to obtain a laminated sheet. Then, the drum was kept at a surface temperature of 20 ° C., and was closely cooled and solidified by an electrostatic application method to obtain an unoriented (unstretched) laminated sheet. When the cross section of the obtained single layer film was observed, it was found that PMP was dispersed with a volume average particle size of 2.5 μm.

  Subsequently, after preheating the unstretched monolayer film with a roll group heated to a temperature of 85 ° C., using a heating roll having a temperature of 90 ° C., the rolls are rolled between the rolls at a magnification described in Table 2 in the longitudinal direction (longitudinal direction). The film was stretched and cooled with a roll group at a temperature of 25 ° C. to obtain a uniaxially oriented (uniaxially stretched) film. The obtained uniaxially oriented (uniaxially stretched) film is guided to a preheating zone at a temperature of 95 ° C. in the tenter while holding both ends of the film with clips, and continuously in a heating zone at a temperature of 105 ° C. in a direction perpendicular to the longitudinal direction ( In the width direction), the film was stretched at a magnification described in Table 2. Subsequently, a heat treatment was performed at 240 ° C. for 20 seconds in a heat treatment zone in the tenter, and after a relaxation treatment in the 4% width direction at a temperature of 200 ° C., a further 1% width direction at a temperature of 140 ° C. A relaxation treatment was performed. Subsequently, after uniform cooling, the film was wound up to obtain a biaxially oriented polyester film having a total film thickness of 100 μm and a main extruder component layer (ie, ID layer) thickness of 80 μm. Table 2 shows the results of observing the cross section of the obtained film. A large number of flat diffusing elements (d1) were contained as diffusing elements (D) inside the film (that is, inside the ID layer). In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. It was found that the surface light source was excellent in luminance, and in particular, when the film of the present invention was installed directly on the diffusion plate, it was the surface light source with the highest luminance, uniformity, and display quality. Further, although moire was confirmed, good display quality could be obtained if a general back coat layer was formed.

(Examples 2 to 27)
Except for using the mixture of raw materials shown in Table 1 and the composition, conditions, and thickness shown in Table 2, the same methods as in Example 1 were used, and 2 to 21, 25 to 26 had a total film thickness of 100 μm. , A biaxially oriented polyester film having a main extruder component layer (ie, ID layer) thickness of 80 μm, Example 22 has a total film thickness of 188 μm, and a main extruder component layer (ie, ID layer) thickness of 150 μm A biaxially oriented polyester film, Example 23 has a total film thickness of 62.5 μm, a main extruder component layer (ie, ID layer) has a thickness of 50 μm, and Example 24 has a total film thickness of Example 24. A biaxially stretched film having a thickness of 31.3 μm and the thickness of the component layer (namely, ID layer) of the main extruder was 25 μm was obtained. Table 2 shows the results of observing the cross sections of the master batch, unstretched film, and biaxially stretched film. A large number of flat diffusion elements (d1) were contained as diffusion elements (D) inside the biaxially stretched film (that is, inside the ID layer). In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. It was found that the surface light source was excellent in luminance, and in particular, when the film of the present invention was installed directly on the diffusion plate, it was the surface light source with the highest luminance, uniformity, and display quality. Further, although moire was confirmed, good display quality could be obtained if a general back coat layer was formed.

(Example 28)
A biaxially stretched film was obtained in the same manner as in Example 1 except that a master chip was not produced and a mixture having the composition shown in Table 2 dried at 140 ° C. for 8 hours was directly introduced into a single screw extruder. Table 2 shows the results of observation of the cross sections of the unstretched film and the biaxially stretched film. A large number of flat diffusion elements (d1) were contained as diffusion elements (D) inside the biaxially stretched film (that is, inside the ID layer). In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. Although it was inferior to Example 1, it was found to be excellent in luminance. In particular, when the film of the present invention was installed immediately above the diffusion plate, it was found that the surface light source had the highest luminance, uniformity, and display quality. Further, although moire was confirmed, good display quality could be obtained if a general back coat layer was formed.

(Example 29)
What was mixed so that it might become the same composition using the masterbatch of Example 1 was vacuum-dried at the temperature of 180 degreeC for 2 hours, Then, it supplied to the main extruder. Further, a single-layer unstretched sheet and an internal diffusion layer (ID) layer having a thickness of 80 μm were formed in the same manner as in Example 1 except that only the main component layer was extruded as a single layer without using a sub-extruder. A biaxially oriented polyester film consisting of layers was obtained. As a result of observing the cross section of the masterbatch, unstretched film, and biaxially stretched film, it contains a flat diffusing element (d1) as the diffusing element (D) inside the ID layer of the biaxially stretched film. It was the same form as Example 1. In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. It was found that the surface light source was excellent in luminance, and in particular, when the film of the present invention was installed immediately above the diffusion plate, the surface light source had the highest luminance and excellent uniformity. Also, good display quality could be obtained without forming a backcoat layer.

(Example 30)
Component layer supplied to sub-extruder on one side surface layer of component layer supplied to main extruder in thickness ratio Sub-extruder component layer: main extruder component layer = 1: 9 That is, other than ID layer thickness / ID layer The entire film was formed in the same manner as in Example 1 except that the sum of the thicknesses of the layers (S layer) was combined to be 1/9, and melted two-layer lamination coextrusion was performed from within the T die die. A biaxially oriented polyester film having a thickness of 90 μm and a thickness of the main extruder layer (ie, ID layer) of 80 μm was obtained.
As a result of observing the cross section of the masterbatch, unstretched film, and biaxially stretched film, it contains a flat diffusing element (d1) as the diffusing element (D) inside the ID layer of the biaxially stretched film. It was the same form as Example 1.
In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. It was found that the surface light source was excellent in luminance, and in particular, when the film of the present invention was installed immediately above the diffusion plate, the surface light source had the highest luminance and excellent uniformity. Also, good display quality could be obtained without forming a backcoat layer.

(Examples 1-2 to 28-2)
Using the biaxially oriented polyester film obtained in Examples 1 to 28 as a base film, one side of the base film was subjected to corona treatment. Next, the coating agent adjusted by the following method was apply | coated to the surface which implemented the corona treatment surface using the metabar (# 20). After coating, the film was dried at 100 ° C. for 30 seconds and heat treated at 150 ° C. for 10 seconds to form a light diffusion layer having a dry thickness of 15 μm on the polyester film. The appearance of the obtained light diffusing layer was good without unevenness being confirmed. Table 3 shows the results of measuring the luminance using the obtained film. Compared with Examples 1 to 28 in which no light diffusion layer is formed, the luminance and luminance unevenness are excellent, and in particular, the surface of the side on which the film of the present invention is installed directly on the diffusion plate and the light diffusion layer is not formed. It was found that the surface light source had the highest brightness and excellent uniformity when facing the diffuser plate. Although moire was confirmed, good display quality could be obtained if a general backcoat layer was formed on the surface opposite to the surface on which the light diffusion layer was formed.

(Coating agent adjustment)
65 parts by mass of “Aronix” (registered trademark) M6050 (manufactured by Toagosei) as binder resin, 5 parts by mass of “Aronix” (registered trademark) M5700 (manufactured by Toagosei), and “Chemisnow” (registered trademark) MX-1500 (as fine particles) 30 parts by weight (manufactured by Soken Chemical Co., Ltd.), “Marialim” (registered trademark) AKM-0531 (manufactured by Nippon Oil & Fats Co., Ltd.) 0.5 part by weight as a dispersant, “Kaya Ester” (registered trademark) as a thermal polymerization initiator ) 0.5 parts by mass of AN (manufactured by Kayaku Akzo Co., Ltd.) and 200 parts by mass of cyclohexanone / methyl ethyl ketone = 1/1 (mass ratio) solution as a solvent are mixed and stirred to prepare a coating material in which fine particles are dispersed. did.

(Example 29-2)
A light diffusion layer was formed in the same manner as in Example 1-2, except that the polyester film obtained in Example 29 was used as the base film. The obtained light diffusion layer was partially confirmed to be coated and repelled.
Table 3 shows the results of measuring the luminance using the obtained film. Compared with Example 29 in which the light diffusion layer is not formed, the brightness and luminance unevenness are excellent. In particular, the film of the present invention is installed directly on the diffusion plate, and the surface on which the light diffusion layer is not formed is the diffusion plate. It was found that the surface light source with the highest brightness and excellent uniformity was obtained. Also, good display quality could be obtained without forming a backcoat layer.

(Example 30-2)
A light diffusion layer was formed in the same manner as in Example 1-2, except that the polyester film obtained in Example 30 was used as the base film. When the obtained light diffusing layer was formed on the inner diffusion layer (ID) layer side, the application repelling was partially confirmed, but when it was applied on the S layer side, the appearance of the obtained light diffusing layer was uneven. Was not confirmed and was good. Table 3 shows the results of measuring the luminance using a film having a light diffusion layer formed on the S layer side. Compared with Example 30 in which no light diffusion layer is formed, it is excellent in luminance and luminance unevenness, and in particular, the film of the present invention is placed immediately above the diffusion plate, and the surface on which the light diffusion layer is not formed is the diffusion plate It was found that the surface light source with the highest brightness and excellent uniformity was obtained.

(Examples 1-3 to 28-3)
Examples 1-3 to 21-3 are the same as Examples 1-28 except that 15 mol% naphthalenedicarboxylic acid copolymerized PET is used as a raw material for the component layer (that is, resin layer S layer) of the sub-extruder. 25-3 to 28-3 is a biaxially oriented polyester film having a total film thickness of 100 μm and a main extruder layer (ie, ID layer) of 80 μm. Example 22-3 has a total film thickness of 188 μm. , A biaxially oriented polyester film having a main extruder component layer (ie, ID layer) thickness of 150 μm, Example 23-3 has a total film thickness of 62.5 μm, the main extruder component layer (ie, ID layer) A biaxially oriented polyester film having a thickness of 50 μm, Example 24-3 is a biaxially oriented polyester film having a total film thickness of 31.3 μm and a main extruder component layer (ie, ID layer) thickness of 25 μm. A reester film was obtained. The biaxially stretched film and the mold are laminated with the uneven surface of the mold 1 having the following shape on the S layer on one side of the obtained biaxially stretched film and the mold 2 having the following shape on the other surface. Heated to 120 ° C., pressed at 20 MPa, and held for 2 minutes. Thereafter, the press was released after cooling to 70 ° C., cooled to 30 ° C. and released from the mold.
(Mold 1)
A dome-shaped projection with a close-packed arrangement (FIG. 19A) inverted (the cross-sectional shape of the dome-shaped projection is FIG. 19B)
(Mold 2)
The shape of the back coat surface of the diffusion film GM3 manufactured by Kimoto Co., Ltd. is inverted by electroforming.
As a result of observing the cross-sectional shape of the obtained film, it was found that the shape of the mold was successfully transferred except for Example 21-3.
Table 4 shows the results of measuring the luminance using the obtained film. Except for Example 21-3, it is excellent in luminance and luminance unevenness as compared with the case where the light diffusion layer is not formed (Examples 1 to 28). In particular, the film of the present invention is installed directly on the diffusion plate, and light is emitted. It was found that when the surface on which the diffusion layer is not formed is opposed to the diffusion plate, the surface light source has the highest luminance and excellent uniformity. Also, good display quality could be obtained without forming a backcoat layer.

(Example 30-3)
Except for using 15 mol% naphthalenedicarboxylic acid copolymerized PET as a raw material for the component layer (ie, resin layer S layer) of the sub-extruder, the thickness of the entire film is 90 μm in the same manner as in Example 1-3. A biaxially oriented polyester film having a thickness of the component layer (ie, ID layer) of 80 μm was obtained.
Next, the shape of the mold 1 was transferred to the S layer in the same manner as in Example 1-3 except that the mold 2 was not used.
As a result of observing the cross-sectional shape of the obtained film, it was found that the shape of the mold 1 was successfully transferred. Table 4 shows the results of measuring the luminance using the obtained film. Except for Example 21-3, it is excellent in luminance and luminance unevenness as compared with the case where the light diffusion layer is not formed (Example 30), and in particular, the film of the present invention is installed immediately above the diffusion plate, and the light diffusion layer It was found that the surface light source with the highest luminance and excellent uniformity was obtained when the surface on which the surface was not formed was opposed to the diffuser plate. Also, good display quality could be obtained without forming a backcoat layer.

(Reference example)
The ID layer of Example 29 and the S layer of Examples 1 to 28 and Example 30 were released from the mold after being heated, pressed and cooled by the same mold and method as in Example 1-3.
As a result of observing the cross-sectional shape of the obtained film, it was found that none of the mold shapes could be transferred.
(Comparative Examples 1-6)
A biaxially stretched film was obtained in the same manner as in Example 1 except that the mixture of raw materials shown in Table 1 was used, and the composition, conditions and thickness shown in Table 2 were used. Table 2 shows the results of observing the cross sections of the master batch, unstretched film, and biaxially stretched film. In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. Various characteristics were inferior to those of the examples.

(Comparative Example 7)
A biaxially stretched film was obtained in the same manner as in Example 1 except that a master chip was not produced and only PET-1 dried at 180 ° C. was introduced into a single screw extruder. In addition, Table 2 shows the characteristics of the polyester film and the luminance measurement results. Various characteristics were inferior to those of the examples.

(Comparative Examples 1-2 to 7-2)
A light diffusion layer was formed in the same manner as in Example 1-2 except that the films of Comparative Examples 1 to 7 were used.
Table 3 shows the results of measuring the luminance using the obtained film. Although it was excellent in the brightness | luminance and brightness nonuniformity compared with Comparative Examples 2-1 to 2-7 which did not form the light-diffusion layer, it was a result inferior to various characteristics compared with an Example.

(Comparative Examples 1-3 to 7-3)
The film which laminated | stacked 15 mol% naphthalene dicarboxylic acid copolymerization PET as S layer was obtained by the same method as Comparative Examples 1-7 except having used 15 mol% naphthalene dicarboxylic acid copolymerization PET as a raw material for S layers. The S layer of the obtained laminated film was released from the mold after heating, pressing and cooling by the same mold and method as in Example 1-3.

As a result of observing the cross-sectional shape of the obtained film, it was found that all of them were able to transfer the shape of the mold well. However, in Comparative Examples 1-3 to 3-3, it was found that the film was whitened.
Table 4 shows the results of measuring the luminance using the obtained film. In Comparative Examples 1-3 to 3-3, it was found that the luminance was lower than that in which the light diffusion layer was not formed (Comparative Examples 1 to 3). Moreover, in Comparative Examples 4-3 to 7-3, although it was excellent in the brightness | luminance and brightness nonuniformity compared with Comparative Examples 4-7 which have not formed the light-diffusion layer, it was a result inferior to various characteristics compared with an Example. .

  The diffusion sheet of the present invention can be applied as a thin optical member that exhibits high screen uniformity and high luminance characteristics by being incorporated in a surface light source unit of various display devices, particularly liquid crystal display devices.

1: Diffusing element (d1)
2: One end (left end) of the diffusing element (d1) in a direction parallel to the film surface direction
3: The other end (right end) of the diffusing element (d1) in a direction parallel to the film surface direction
4: Line segment (major axis) connecting one end (left end) 2 of the diffusing element (d1) and the other end (right end) 3 of the diffusing element (d1)
5: Midpoint of line segment 6: One end (upper end) of diffusion element (d1) passing through midpoint 5 and on a line perpendicular to line segment 4
7: One end (lower end) of the diffusing element (d1) passing through the midpoint 5 and on the line perpendicular to the line segment 4
8: Line segment (short axis) connecting one end (upper end) 6 of the diffusing element (d1) and the other end (lower end) 7 of the diffusing element
2 ': One end (left end) of the diffusing element (d1) in a direction parallel to the film longitudinal direction
3 ′: The other end (right end) of the diffusing element (d1) in the direction parallel to the film longitudinal direction
4 ': A segment (long axis) connecting one end (left end) 2 of the diffusing element (d1) and the other end (right end) 3 of the diffusing element (d1)
5 ': Midpoint 6' of line segment 4 ': One end (upper end) of diffusion element (d1) passing through midpoint 5' and on a line perpendicular to line segment 4 '
7 ′: One end (lower end) of the diffusing element (d1) passing through the midpoint 5 ′ and on a line perpendicular to the line segment 4 ′
8 ′: A segment (short axis) connecting one end (upper end) 6 ′ of the diffusing element (d1) and the other end (lower end) 7 ′ of the diffusing element (d1)
10: Reflector 11: Housing 20: CCFL
30: Diffuser plate 40: Optical film group 41: First optical film 42: Second optical film 43: Third optical film 100: Diffusion element 200: Matrix 300: Binder resin 400: Fine particles 500: Concave and convex shape λ0: Incident light λ1: Light transmitted through the diffusing element 100 λ2: Light reflected at the interface between the matrix resin and the diffusing element and scattered toward the incident direction side λ3: Reflected / refracted at the interface between the matrix resin and the diffusing element and perpendicular to the incident direction Light λ3 ′ scattered in the vicinity: Light scattered by the diffusing element and emitted to the side surface and lost x: Film longitudinal direction y: Film width direction z: Film thickness direction

Claims (13)

A film having a layer made of a matrix resin containing a diffusion element (D) (hereinafter referred to as an internal diffusion layer (ID layer)), the total number of diffusion elements (D) included in the internal diffusion layer (ID layer) The ratio of the number satisfying the following (1) and (2) of the diffusion element (d1) is 50% or more, and the number of the diffusion elements (D) included in the internal diffusion layer (ID layer) in the film thickness direction is 3. A light diffusing film, wherein the number is from 120 to 120.
(1) The absolute value | Nm−Nd | of the difference in refractive index between the refractive index Nm of the matrix resin constituting the internal diffusion layer (ID layer) and the refractive index Nd of the diffusion element (d1) is 0.05 or more and 0.00. 3 or less.
(2) The flatness is 3 or more and 100 or less. The light diffusion film according to claim 1, wherein the number of diffusion elements (D) per 10 μm length in the film thickness direction is 1/10 μm or more and 10/10 μm or less. In a cross section parallel to the film surface, the ratio of the in-plane long axis length of the diffusing element (D) to the in-plane length (in-plane short axis length) perpendicular to the long axis direction (in-plane long axis) The light diffusion film according to claim 1, wherein the length / in-plane minor axis length is 2 or less. The light-diffusion film in any one of Claims 1-3 whose volume occupation rate of the bubble of an internal diffusion layer (ID layer) is 3 volume% or less. The light diffusion film according to claim 1, wherein the internal diffusion layer (ID layer) is biaxially oriented. The light diffusion film according to claim 1, wherein the matrix resin constituting the internal diffusion layer (ID layer) is made of a thermoplastic resin containing a polyester resin. The light diffusing film according to claim 1, wherein the diffusing element (d1) is made of a thermoplastic resin. The light diffusion film according to claim 7, wherein the diffusion element (d1) is a polyolefin-based resin. The light diffusion film according to claim 1, wherein the surface free energy of at least one surface is 35 mN / m or more. The resin layer (S layer) is laminated on one side or both sides of the internal diffusion layer (ID layer), and the difference (Tm1−Tm2) between the melting point Tm1 of the matrix resin and the melting point Tm2 of the resin layer (S layer) is It is 10 degreeC or more, The light-diffusion film in any one of Claims 1-9. The light-diffusion film in any one of Claims 1-10 which has an uneven structure in at least one surface. The light-diffusion film in any one of Claims 1-11 whose total light transmittance is 25 to 80%. The surface light source using the light-diffusion film in any one of Claims 1-12.

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